Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: MBehrens on July 13, 2011, 08:52:22 pm
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I've heard this suggestion from a few experts on White Balance and shooting RAW...
"By setting the White Balance in the camera to a selection other than Auto. You will streamline your post processing by having a static value assigned and not a different value possibly for each image. By having a static setting for all of the images in a shoot, you can simply apply a new value to all images and be on your way."
I think this is a myth and mis-information that does not help in the understanding of RAW capture and White Balance. My reasoning is that since ACR/LR (the subject by the experts and my choice) will apply a WB value when syncing that is not in anyway affected by the WB setting from the camera, whether WB is different for each image or the same makes no difference. The WB setting in the camera has no affect on the RAW capture so there isn't any change to the RAW data from the setting, if it did I can see how it would provide a more consistent set of RAW files - but it doesn't.
Frankly, I mostly shoot RAW and I always use Auto-WB when I do. I think I can sync my WB as easily as the rest. Are the "experts" correct and I'm fooling myself, or am I on the right track, or is there another point of view on this.
I apologize if this has been beaten to death in other threads, I did do a search and did not find anything substantive.
Thanks.
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Frankly, I mostly shoot RAW and I always use Auto-WB when I do.
Me too. Because:
1. It doesn’t affect the raw data, its just a suggestion (a guess).
2. The suggestion/guess is usually pretty OK and I usually season a bit to taste.
3. Its less work (I’m lazy).
4. Even if its just OK, its usually OK enough for quick viewing as I edit, then I’ll concentrate on tweaking as the need arises.
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3. Its less work (I’m lazy).
My primary driver as well. And it seemed when I did set a WB it was usually farther off than the Auto choice.
Not sure what these folks are thinking. One was at a color management web cast, made me question everything they told me.
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I also shoot RAW with Auto White Balance, and sometimes shoot a gray card in the same light in case I want to use it for white balance values.
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sometimes shoot a gray card in the same light
I find I'm shooting a gray card less and less. It's just another reference point en route to a final choice. Since it's seldom the final choice it ends up being an extra step.
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Hi,
Same here, I shoot only in RAW, use auto white balance most of the time. For indoor exhibition documentation I will often shot a frame with my x-rite colour checker for each setup as the light illuminating the works can be a mish-mash of different age galley lights and most often supplemented by my own hot lights. Using the colour checker lets me reproduce the correct ochre or whatever else is in the original works. Still, far easier than calibrating the same in a chemical darkroom.
Jean-Michel
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"By setting the White Balance in the camera to a selection other than Auto. You will streamline your post processing by having a static value assigned and not a different value possibly for each image. By having a static setting for all of the images in a shoot, you can simply apply a new value to all images and be on your way."
I think this is a myth and mis-information that does not help in the understanding of RAW capture and White Balance. My reasoning is that since ACR/LR (the subject by the experts and my choice) will apply a WB value when syncing that is not in anyway affected by the WB setting from the camera, whether WB is different for each image or the same makes no difference. The WB setting in the camera has no affect on the RAW capture so there isn't any change to the RAW data from the setting, if it did I can see how it would provide a more consistent set of RAW files - but it doesn't.
Frankly, I mostly shoot RAW and I always use Auto-WB when I do. I think I can sync my WB as easily as the rest. Are the "experts" correct and I'm fooling myself, or am I on the right track, or is there another point of view on this.
I apologize if this has been beaten to death in other threads, I did do a search and did not find anything substantive.
Thanks.
I also usually use auto WB on my Nikon D200 and D3, but one must remember that the camera looks at the image and not the color of the light. Some older Nikon DSRs did have a sensor to read the ambient light, but none that I know about do at the present.
If the subject has a strong color cast (for example a close up of a brightly colored flower) and no neutrals in the scene, auto WB may not work well. In such cases, it is a good idea to use a Whibal or similar reference to read the white balance. You can adjust the WB in post, but you will have to rely on memory to match the image to the original. This is most important for scientific documentation where you want the color to be as accurate as possible and not merely pleasing. You could merely use daylight, but the color of daylight varies with the time day, atmospheric conditions and other factors.
Regards,
Bill
See the Cambridge in Color tutorial on white balance (http://www.cambridgeincolour.com/tutorials/white-balance.htm) for more information.
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I always use the auto setting and sometimes adjust the wb in RAW. But I always use a Wibal or similar card when shooting color critical work such as an artist's canvas to make prints for resale. Then one touch of the eyedropper on the card in RAW and I've got it right 99% of the time.
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The only place I don't shoot auto white balance is at basketball games. I have known consistent lighting conditions there and set up a custom white balance that gets JPEGs (written to an SD card) "close enough" for quick edits by the team at halftime. All the final images are RAWs that are processed in LR with custom presets that do white balance and whatnot.
Neil
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Thanks folks. My assumptions are confirmed, and of course for color critical work a gray card or color checker is a must.
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I generally shot in AWB, the exception is when I am shooting studio strobes and the modeling lights will throw off the white balance; in that case is set the WB using a grey card. But the only reason to do that is so that the intitial view in Bridge/ACR is not way off color wise; I could of course just apply a batch adjustment to all images.
Since I what I shoot otherwise is urban landscapes and not products or art, proper WB for me I how I want the print to look; so precise matching is never an issue anyway.
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Shoot a multi-image pano during sunrise or sunset with the WB set to auto and after you try to fix it in ACR, you will probably be cured of setting the WB to auto. :)
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Justan, I'm not clear how having the camera record a WB suggestion/default of say 5K and this be the initial rendering of the RAW data in ACR. And applying a WB of 5K or any other value, in ACR is going to make a difference. The RAW data is the same irrespective of what the initial WB suggestion from the camera is. Please explain.
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Unlike most people (as seen in this thread) I never use Auto WB because it doesn't mean any advantage to me. You can always set Auto WB in your RAW developer, and OK, maybe the camera's Auto WB performs better than the RAW developer's Auto WB for a particular scene, but who cares?. After all Auto WB is ALWAYS a best effort approximation (http://www.guillermoluijk.com/article/wb/index.htm), it will never be exactly the best possible WB.
On the other hand, other WB options really mean advantages:
- Preset WB according to the scene: will guarantee the same WB in a series of pictures. Auto WB will vary from picture to picture.
- Custom WB over a gray card: will certainly eliminate light casts revealing the real colour of subjects in the scene, and will also guarantee uniform WB in a series.
- UniWB (http://www.guillermoluijk.com/tutorial/uniwb/index_en.htm): will provide a much more accurate camera histogram and clipping warning.
Auto WB is an easy option and maybe a good start point for a more accurate WB setting, but the only one without any real advantage.
Regards
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Justan, I'm not clear how having the camera record a WB suggestion/default of say 5K and this be the initial rendering of the RAW data in ACR. And applying a WB of 5K or any other value, in ACR is going to make a difference. The RAW data is the same irrespective of what the initial WB suggestion from the camera is. Please explain.
If a camera is set to auto wb and one captures multiple frames near twilight -when the light color changes very quickly - each image will have a different wb due to the way the sensor interprets the changes of light.
When stitched together, smooth tonal gradients from image to image are trashed. One can try to re-set the WB for each image in ACR, or one can use ACR’s synchronize function, but the results won’t be as desired without a fair amount of work.
The solution that worked for me was to lock the WB in the camera. Once I did that, the anomalies mentioned above ended. Try it for yourself. If one never does stitches or stacks, then it’s not much of an issue.
ACR, PS, or their equivalents can fix nearly anything, but its way quicker to get it right in the camera.
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I used to use Auto WB but more recently have been using a grey card for Custom WB, both in the studio and in the field, then tweak to taste if necessary. I know it's just a suggestion but, also being lazy, I find it gets me there quicker (I had a girlfriend like that once!) I may shoot the card a couple of times if shooting outside all day long though.....
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I checked the total time needed for my last few panorama shots (in auto WB) and found an elapsed time of just 5-10 seconds over 3-5 exposures. I've never had a problem with light changing that quickly.
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I checked the total time needed for my last few panorama shots (in auto WB) and found an elapsed time of just 5-10 seconds over 3-5 exposures. I've never had a problem with light changing that quickly.
The problem is not light changing with time, but changing with the angle of vision. Each of your panorama shots obtained a (probably slightly) different Auto WB calculation because each of them had a different content from which the camera software made its calculations.
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The problem is not light changing with time, but changing with the angle of vision. Each of your panorama shots obtained a (probably slightly) different Auto WB calculation because each of them had a different content from which the camera software made its calculations.
Good point. But I'm afraid my 70+ year old eyes couldn't tell that fine a difference. Still, I'll try a few tests (auto wb vs locked wb) next time I'm shooting, probably tomorrow. I'm thinking if I eye-dropper the same spot in each shot (say, in the overlapping area) I may get a different r g b reading. ??? Just thinking out loud.
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I nearly always keep the back in Daylight and adjust in C1 as needed. When the light is questionable a WhiBal shot provides a guideline.
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When I shoot a panorama, I use preset white balance - set this by pointing the camera at the light source with a BaLens cap and set the white balance. I set the camera in manual mode, use autofocus to focus the lens and then turn it to manual. If I shoot multi row panorama, I generally turn on auto focus for the bottom row since objects are much closer than the top two rows. I shoot panoramas with the camera in portrait mode. Lens is generally 105mm and most images require 3 rows of 6 images each. Image is saved in RAW format and I process using Photoshop CS5 ACR RAW comverter. Since exposure and white balance are identical in each image, I select one of the images in ACR and then select all and adjust all at the same time.
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I checked the total time needed for my last few panorama shots (in auto WB) and found an elapsed time of just 5-10 seconds over 3-5 exposures. I've never had a problem with light changing that quickly.
That would work for just 3-5 exposures.
For most of the pano's I shoot, using a spherical pano head I'm doing vertical columns of as many as 5-6 frames, with 10 to 12 horizontal frames with a 85mm lens. Add in HDR and now you have three exposures per frame, setting a custom WB is essential.
Working fast, it could take 30 to 40 min, that said, your not going shoot pano's this big as the sun is setting.
Depending on how late in the day, and how fast the light is changing, by shooting vertical columns, adjusting exposure as you go from column to column has worked for me, but with AWB would it will fail
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When I shoot a panorama, I use preset white balance - set this by pointing the camera at the light source with a BaLens cap and set the white balance. I set the camera in manual mode, use autofocus to focus the lens and then turn it to manual. If I shoot multi row panorama, I generally turn on auto focus for the bottom row since objects are much closer than the top two rows. I shoot panoramas with the camera in portrait mode. Lens is generally 105mm and most images require 3 rows of 6 images each. Image is saved in RAW format and I process using Photoshop CS5 ACR RAW comverter. Since exposure and white balance are identical in each image, I select one of the images in ACR and then select all and adjust all at the same time.
I'm missing something here. Since the white balance setting (preset or otherwise) doesn't affect the RAW data and ACR doesn't pickup any white balance setting from the camera, what's the point of setting this preset?
--Milt--
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I'm missing something here. Since the white balance setting (preset or otherwise) doesn't affect the RAW data and ACR doesn't pickup any white balance setting from the camera, what's the point of setting this preset?
Actually, ACR/LR DOES pick up WB settings in the raw file. What it DOES with them is, however usually different than what the camera makers software would do since ACR/LR's white balance is unique...setting a fixed WB in camera would prolly be better for panos than letting the camera adjust the WB using auto. Note, you are correct that the WB setting in camera is simply a metadata tag and can be overridden in ACR/LR. That takes only a bit of work to WB one of the pano images and sync to the rest of the captures. So it's more efficient to not worry about WB when shooting and adjust it in the raw processing before the pano is done...
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Hmm. I think I'm learning something new here. Are you saying that ACR does pick up the information from a camera white balance preset and make it available for use during processing? If so, and if that camera preset were established as suggested by a baLens (or a card), then that's a piece of information about the shooting conditions that isn't otherwise available during processing. Also, is ACR able to do this for a pretty wide variety of modern cameras?
--Milt--
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Hmm. I think I'm learning something new here. Are you saying that ACR does pick up the information from a camera white balance preset and make it available for use during processing?
It reads the "As shot" white balance settings from the EXIF data and uses that as a startingpoint.
Cheers,
Bart
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I found this old topic after a discussion with a friend of mine. He insisted that my way of using Raw and Auto in camera settings is not the proper way. He uses a Color Temperature Meter and adjusts white balance in LR if necessary. I have been quite happy with using Auto so far. Sometimes I have changed the white balance a bit, but most of the time I have accepted the white balance suggested by Adobe ACR.
Today I made a simple test taking two raw images, one with Auto and one with Daylight. I processed the raw images in Adobe ACR and to my astonishment Daylight gave better result than Auto. It was a sunny day and I made the test in the middle of the day. The difference was not big, but the difference was easy to see.
Maybe I have to make new tests...
(Canon 5dmkII, Canon EF 24-105 f/4, Bridge CS4 3.0.0.464, ACR 5.7.0.213)
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Maybe I have to make new tests..
I think so as the WB has no effect on the raw data. The suggestions made do in terms of what you initially see but you can over-ride that at any time. IOW, the metadata affects the converter, not the raw data.
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Of course it hasn't. It's all about guessing or determining the 'starting point'.
As Guillermo Luijk writes in one of articles: "La conclusión es que no puede existir un balance de blancos automático que emule bien en cualquier situación el balance que hace nuestro cerebro"
"The conclusion is that there can be no automatic white balance that emulates good balance in any situation that makes our brain." (Translation by google, not mine...)
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White balance has become one of those subjective evaluations that has been taken to extremes, especially in the stock photography business. I have had dozens of otherwise acceptable images refused because "...white balance may be incorrect". What that often means is that the reviewer doesn't like something about the image that he/she can't quite put a finger on. On the rejected images I often go back and double check my work flow and, sure enough, the white balance is perfect. My conclusion is that many reviewers live in climates other than mine (Arizona) and are not used to seeing really brillant sun and the colors that result, especially in landscape scenes. The same rejections often occur in low-light situations when the reviewer hasn't experienced that particular light condition and thus it must be "incorrect white balance."
Thankfully I've since ceased to worry about outside evaluations on this subject and simply process my images as I see fit.
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AWB is almost always "right". Anyway, as others have said, you can post-process raw data as you wish but the archetypal example is the candle light dinner. Technically correct white balance with yield hospital like shots, but we all know that the yellowish AWB default settings come up with is the good one :-)
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AWB is almost always "right".
No...it's often close but usually requires tweaking and this is really camera dependent. nFor example, AWB on a Phase One back sucks big ones...similar to Panasonic and other lesser brands (it's ok, I've got a GH2). But Nikon and Canon AWB is close but expect to optimize it series by series.
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Then you get into the issue of what influences the proper appearance of WB shooting in 2800K tungsten or sunset. It can mess up your perception during WB tweaks when you're not quite sure if the color cast of the surface in question is being influenced by the color cast of the light source OR by the spectral reflectance characteristic of the surface itself as I tried to point out in this thread...
http://photo.net/beginner-photography-questions-forum/00ZUlB
The OP specifically states the japanese woman was wearing white-ish makeup lit by the setting sun shot outdoors but she kept indicating no matter what she did with WB in her Raw processor the image just wasn't looking right. You'll note my demo edits didn't result in the make up looking white at all. I suspected the white pancake makeup lit by the setting sun reflected back something the camera recorded but the eyes did not see.
Would you say this is one situation WB shooting Raw did have some influence on the Raw data or maybe the processor? I was thinking she should've chosen "tungsten" WB preset within her camera to correct for the white makeup.
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No...it's often close but usually requires tweaking
This is the lesson I learned. I have routinely accepted ACR's suggestion. From now on I will try focus more on white balance in ACR:
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The right WB is many times subject to discussion. What is the definition of a right WB?
- The one that allows to see the real colour of objects?
- The one that reminds us better the feeling we had at taking the picture?
- The one that pleases most our eyes?
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There could be 3 different WB settings for those 3 definitions. IMO the right WB depends on the application. Just an example:
(http://www.guillermoluijk.com/article/wb/ferraricac.jpg)
If you are so lucky to have Ferrari as a customer, they will demand a precise Ferrari red colour for their catalogue. The right WB here will be the one that provides the real colour of the Ferrarri. So using a custom WB over a neutral gray card will be the right WB.
If we are taking more emotional pictures of a warm sunset over a white building, we don't want the building to look white (its real colour) in the final image, but preserve some of the warm atmosphere. In this case a gray card would ruin our WB, and we would obtain the right WB by just tweaking it on the RAW developer to match the light and feelings we recall from the scene.
Two different ways to achieve the right WB. None of them would have worked in both situations.
Regards
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I have noticed that when I change the WB setting in ACR to different settings then the exposure changes thus affecting the histogram. If it changes in ACR then the setting chosen in camera will affect the histogram because it is a jpeg histogram. So choosing a WB in camera does make a difference?
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The right WB is many times subject to discussion. What is the definition of a right WB?
Exactly.
Imagine staying inside a candle-lit cabin with your friends late in the evening at winter-time. Look out the window and you may see a snow-clad landscape with an effective color-temperature that is very different from inside the cabin (i.e. outside the "whites" are "blueish", while inside the whites are yellowish). Do you or any of your friends complain about the white-balance of the window or of nature being "wrong"? Of course not, they (subconsciously) seem to accept that the illumination outside is different, and as a consequence the color balance is shifted.
What happens if you take a picture of that scene, print it and hang it on the wall of the same cabin? Say that you have a camera workflow that prioritize "engineering philosophy", i.e. recreating the color perfectly within the predefined CIE space. How would that image look under similar conditions? Would you and your friends think that it had a blue cast?
I have tried to use this analogy to get a better grip at what WB really is and what people expect it to do. To me it seems that most people want WB to "move them into the scene". I.e. alter the WB of the image in such a way that the viewer perceives it the same way as if he had been there (assuming perceptual adaptive processes) if it is to fill the entire field of vision, and/or that it is a natural extension to however the viewing environment (lighting, roof, walls,...) is. I.e. i the viewing environment is yellow-cast, the viewers adapt to that white-point, and expect the image to have a similar white-point (under the same illumination - directly lit displays is perhaps more difficult)
-h
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AWB is almost always "right". Anyway, as others have said, you can post-process raw data as you wish but the archetypal example is the candle light dinner. Technically correct white balance with yield hospital like shots, but we all know that the yellowish AWB default settings come up with is the good one :-)
I am seldomly happy with the AWB of my Canon SLR. It does not bother me that much because I can rapidly find something better using either the WB "picker", or just tweaking the settings for a group of pictures taken under the same lighting conditions.
The most difficult is when a face/skin dominate the image, no "neutral whites" are present, and the background is dark/grey. For those cases, I wish there was a "skin tone picker" that let me mark the position of human skin, and then apply WB that made it match some averaged human skin chromaticity - as a starting point.
-h
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The selected camera profile can greatly affect the appearance of perceived WB in combination with adjusting the temp/tint WB sliders in ACR/LR.
With my camera Adobe Standard profile neutralizes the entire tonal scale with tungsten lit scenes that may look too yellow amber at default WB. With the right warm hue of overall WB this profile can create some unusual de-saturated browns and beige skin tone colors that at first look a saturated orange yellow with the default ACR 4.4 or a custom DNG profile.
Highlights will appear a dull (de-saturated) yellow amber while the rest of the image seems neutral. It completely changes the emotional ambience of the image in unexpected ways depending on the brand and type of tungsten light shot under and adjustments to WB in ACR/LR.
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I am seldom happy with the auto white balance of my Nikon d3x either...and even the exposure.. There needs still some improvement to be made
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I always shoot in RAW and leave the WB set to "Auto". I see no reason to change it in-camera since it's the very first step in my PP workflow. More often than not, I change the WB, even if just a little bit.
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I always shoot in RAW and leave the WB set to "Auto". I see no reason to change it in-camera since it's the very first step in my PP workflow. More often than not, I change the WB, even if just a little bit.
You change the WB as your first step in PP, but what is your white reference? If you were shooting in daylight, you could use daylight, but the color temperature of daylight varies through the day according to the position of the sun. According to measurements by a Kodak scientist (http://www.handprint.com/HP/WCL/color12.html), direct sunlight in the morning or afternoon has a CCT of 4300K whereas that at noon is 5400K. Daylight (a mixture of direct sun and skylight) is 6500K.
To illustrate, here is a shot of a flower taken at 9:37 a.m. on Sept 21 at a position of 42 N latitude using auto WB with the Nikon D3. The calculated zenith distance of the sun was 60 degrees. The camera looks at the actual colors in the image and not the color of the light. Since the image contains no neutral colors, the ACR WB is not accurate; ACR gives 4400K, which is renders the image as too blue.
(http://bjanes.smugmug.com/Photography/White-Balance/i-F55jQzf/0/L/019ACRAsShot-L.png)
Setting the color balance to daylight helps. ACR gives a WB of 5500K.
(http://bjanes.smugmug.com/Photography/White-Balance/i-Bg5LT2B/0/L/019ACRDaylight-L.png)
A more accurate WB can be taken from another image containing a white cloud as a reference point.
(http://bjanes.smugmug.com/Photography/White-Balance/i-D3tvXGw/0/L/027ACRCloudWB-L.png)
One can apply this WB setting to the flower image to obtain a more accurate rendering of the actual appearance of the flower.
(http://bjanes.smugmug.com/Photography/White-Balance/i-SP44wPn/0/L/019ACRCloudWB-L.png)
For accurate colors, it is usually best to take a WB reading from a neutral card such as a WhiBal. One could take several readings throughout day day when shooting at different times. One could set the WB to render the most pleasing colors, but if it is important to have accurate color, a WB reference point is necessary.
Regards,
Bill
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When the word “accurate” is used, especially when we are talking about rendering an output referred image, the hair on the back of my neck raise.
The question should be, what do we have to do, with AWB or not to produce a pleasing WB?. 9 times out of 10, if we followed the accurate numeric route, we’d be unhappy with the image itself. Just WB on a target and I think you’ll see that it often produces results that are in great need of further seasoning of tint and temp sliders to produce a desirable image.
IF you’re referring to scene referred color, by all means use the term accurate and shoot/adjust/measure for accurate values. The image will look butt ugly but that’s to be expected; its scene referred!
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When the word “accurate” is used, especially when we are talking about rendering an output referred image, the hair on the back of my neck raise.
The question should be, what do we have to do, with AWB or not to produce a pleasing WB?. 9 times out of 10, if we followed the accurate numeric route, we’d be unhappy with the image itself. Just WB on a target and I think you’ll see that it often produces results that are in great need of further seasoning of tint and temp sliders to produce a desirable image.
IF you’re referring to scene referred color, by all means use the term accurate and shoot/adjust/measure for accurate values. The image will look butt ugly but that’s to be expected; its scene referred!
Sorry to hear that my post caused the hair on the back of your neck to raise, but the fact is that AWB with most cameras will not be good if the scene contains no neutrals as explained by Sean McHugh (http://www.cambridgeincolour.com/tutorials/white-balance.htm) on his tutorial. Most cameras look only at the image to obtain WB, and if the image contains a dominant saturated color, the WB will be thrown off.
The fact is that the AWB in the example that I posted is too blue. How would you handle this situation?
Regards,
Bill
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Sorry to hear that my post caused the hair on the back of your neck to raise, but the fact is that AWB with most cameras will not be good if the scene contains no neutrals as explained by Sean McHugh (http://www.cambridgeincolour.com/tutorials/white-balance.htm) on his tutorial.
Not good? Not “accuate”? Not pleasing? FWIW, I find AWB on my Canon’s is pleasing more often than not. Accurate? Not the right term to use here. What you may find pleasing, I may not. Its subjective! Post #34 from Guillermo summed it up prefectly.
The fact is that the AWB in the example that I posted is too blue. How would you handle this situation?
Its YOUR picture so if YOU think its too blue, atler the rendering. Its not MY picture nor do I find it too blue. But its not my picture so my opinion in terms of the color is far less important. ITS SUBJECTIVE, which has nothing to do with accuracy.
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There are times when an 'accurate' WB is necessary. No question about that. But in many cases 'pleasing' is more important than accurate. I don't give a rat's patootie what a Kodak scientist measured as the accurate colour temperature of daylight in early morning. If the 'accurate' white balance doesn't produce a pleasing image then it doesn't matter. And all the measurbatory machinations in the world aren't going to change that.
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Not good? Not “accuate”? Not pleasing? FWIW, I find AWB on my Canon’s is pleasing more often than not. Accurate? Not the right term to use here. What you may find pleasing, I may not. Its subjective! Post #34 from Guillermo summed it up prefectly.
As per Guillermo's post, the objectives for white balance can vary. In my case, I wanted to reproduce the color appearance of the flower as it appeared at the time of the capture. Such a reproduction would be useful to botanists and such a reproduction would be desirable for scientific work. This is analogous to reproducing the red Ferrari in Guillermo's example, where he states that the object of the white balance is "The one that allows to see the real colour of objects". In this case, he suggests that a custom WB from a neutral gray card should be used. If you want to reproduce the subjective appearance of a sunset, another approach would be needed. You might even add saturation and adjust the colors to what you would like an ideal sunset to appear.
Its YOUR picture so if YOU think its too blue, atler the rendering. Its not MY picture nor do I find it too blue. But its not my picture so my opinion in terms of the color is far less important. ITS SUBJECTIVE, which has nothing to do with accuracy.
Since you were not there when the capture was made, you have no idea of the appearance of the flower. You could adjust the WB to obtain what you consider most pleasing, but you could not reproduce the actual appearance of the flower. It is not subjective.
Regards,
Bill
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When the word “accurate” is used, especially when we are talking about rendering an output referred image, the hair on the back of my neck raise.
IF you’re referring to scene referred color, by all means use the term accurate and shoot/adjust/measure for accurate values. The image will look butt ugly but that’s to be expected; its scene referred!
You like to throw about scene referred and output referred imaging, confusing the topic under discussion. As I understand things, a scene referred image represents the actual luminances of the scene. For reproduction, the luminance range in the scene has to be reduced to what can be represented in the viewing medium. If one did linear mapping of a high luminance scene to a photographic print, the print would look flat and very unpleasing. However, the purpose of the output rendering to to map luminances, and the colors should not be affected. However, if the color gamut of the scene exceeded that of the output medium, mapping of the colors might also be needed. For a high dynamic range display, a scene rendered image would look fine.
Regards,
Bill
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In my case, I wanted to reproduce the color appearance of the flower as it appeared at the time of the capture.
Appeared to you as you remember it? In an output referred fashion? You can’t put an accuracy metric* on that. At least one that isn’t subjective. You can say, on a scale of one to ten, ten matching as you recall the scene, this image is X number. But that again is totally subjective. I may have been there with you and disagree. I may only give it a 8. If you want to use accuracy as a useful term, we have to measure the scene color, in which case we are back to scene referred colorimetry. We can then use a non ambiguous, non subjective value to the accuracy.
I can guesstimate the length of the flower in your image below. But that’s a guess, its not accurate. Even if I guess exactly right, until you measure it with something that has a somewhat well defined accurate value (say a good tape measure, using a metric like inches or mm), there is no way either of us can say my guess is accurate or not. Close only counts in (fill in the blank).
Then you say you want to reproduce the color appearance of the flower as it appeared. Reproduced where and how? On a display? Wide gamut or “sRGB”? Or some output device like a print? We’re going to accurately match the gamut, the contrast ratio? Probably not. Again, your idea of a match is subjective. Unless you can measure these attributes and the reproduction, how can we say its accurate? There’s no measurable metric.
IF I measure my display with a sound instrument and it tells me its 150cd/m2, we can use another reference grade device and measure it and determine the accuracy of the first measurement. Otherwise we can look at make a subjective call. But that’s not accurate.
accuracy
n 1: the quality of nearness to the truth or the true value; "he
was beginning to doubt the accuracy of his compass";
"the lawyer questioned the truth of my account" [syn: truth]
[ant: inaccuracy]
* 2: (mathematics) the number of significant figures given in a
number; "the atomic clock enabled scientists to measure
time with much greater accuracy"
Since you were not there when the capture was made, you have no idea of the appearance of the flower. You could adjust the WB to obtain what you consider most pleasing, but you could not reproduce the actual appearance of the flower. It is not subjective.
No I have no idea. But then how do you define my rendering as inaccurate? By how much? A lot? You can say you adjusted the WB to obtain an accurate rendering but how do you prove it? I have to take your word for it. And again, since this is an output referred image, for a specific output referred device, are you quite certain that the same WB and other attributes of the image will retain that exact color and tone on other devices? And if you say yes, how do you prove it.
Accuracy is an over used buzz word. If you are going to say your rendering is accurate, not pleasing or what you believe is a visual match, I’m going to ask you to prove that your use of this WB is indeed accurate. Tell me how you’ll prove this?
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You like to throw about scene referred and output referred imaging, confusing the topic under discussion.
Its only confusing if you don’t understand the terms and the process of imaging. Maybe this white paper from the ICC I co- authored will help (all you have to do is ask):
http://www.color.org/ICC_white_paper_20_Digital_photography_color_management_basics.pdf
The ICC, a group that knows a thing or two about color and color reproduction produced this piece for a reason. They use accuracy metrics all the time. But they don’t confuse subjective from measurable when using the term.
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Its only confusing if you don’t understand the terms and the process of imaging. Maybe this white paper from the ICC I co- authored will help (all you have to do is ask):
http://www.color.org/ICC_white_paper_20_Digital_photography_color_management_basics.pdf
The ICC, a group that knows a thing or two about color and color reproduction produced this piece for a reason. They use accuracy metrics all the time. But they don’t confuse subjective from measurable when using the term.
Thanks for the link, but it adds little to the discussion. The paper confirms what I said about mapping the luminance of the scene to the output medium and does mention that colors (chroma and not hue, I would think) might also need to be mapped. A better discussion of image rendering is given by Karl Lang (http://www.adobe.com/designcenter/dialogbox/karllang/pscs3_rendering_image.pdf).
Regards,
Bill
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A better discussion of image rendering is given by Karl Lang (http://www.adobe.com/designcenter/dialogbox/karllang/pscs3_rendering_image.pdf).
And where in that piece would I find a reference to back up your notion that as you recall the scene, its accurate (and not subjective)?
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does mention that colors (chroma and not hue, I would think) might also need to be mapped.
That’s not a correct assumption in terms of hue. Look at the illustrations and I think you’ll see that all three are affected (camera A and camrea B let alone the sene referred example are different. Just examine the rendering, the WB if you will of the sky). But none the less, you can’t measure A and B to correlate to the scene referred original. You can subjectively say A is closer to your memory.
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And where in that piece would I find a reference to back up your notion that as you recall the scene, its accurate (and not subjective)?
Your assertions can be analyzed by a process of reductio ad absurdum. If effect, you are saying that it is not useful to set or measure the white balance. Throw away the WhiBals and neutral cards. Neglect the white balance eye dropper in ACR. Merely adjust the image to something pleasing. Is that what you mean?
Regards,
Bill
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If you "tweak the sliders until the scene looks good" you are effectively depending on the accuracy of your monitor (and with considerable more delay/cost per iteration: your printer). If you are able to get satisfactory WB based on picking neutral whites, a WB card or similar, one could hope that the unchanged file will only look better as you purchase improved monitors/printers, or improve profiling of the ones that you have.
I think that "recreating reality" is a goal that many aspire to, but only a few really want/need. If you are doing archival of Mona Lisa, you probably want to make the copy appear as close as possible to the original. That means using (incomplete) scientifically based models of human vision and adaptive processes, and trying to recreate that sensation in a different setting. If you (like me) only want to make images that "looks good" for people that wasn't there or cannot remember how the color looked like, you have considerable more freedom. I find that adding a touch of yellow cast often suits my taste.
The concept of "color temperature" rests upon light sources being accurately modelled as a heated blackbody and/or colored reflectors being smooth spectrally, don't it? If the light source is a single-frequency "spike", and the reflectors are similarly erratic, no WB will be able to "correct" the image, and no image sensor whose filters deviate from my personal eye response is going to give me an accurate recreation.
I think that a significant percentage of women actually are sensitive to 4 discrete "primary colors". Last I heard no-one knows if this means that they can make use of that sensory capability to actually perceive more colors. It sure seems like it when one is buying clothes or selecting wallpaint with one... :-)
-h
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Your assertions can be analyzed by a process of reductio ad absurdum. If effect, you are saying that it is not useful to set or measure the white balance.
Where did I say that? In fact just the opposite. I’ve told you I use custom WB to season to taste. What I’m calling you on is your assertion that your subjective setting of WB is accurate. Hogwash I say. It is you that has the burden of proof that your preference for WB is accurate and in anyway correlates to the scene or can be measured. It is you that has the burden of proof that this process is anything but subjective.
Can you provide any scientific methodology to prove your use of WB is accurate and not subjective?
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I think that a significant percentage of women actually are sensitive to 4 discrete "primary colors".
I've read that 2-3% of women are 'tetrachromats'.
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With certain saturated flowers lit close to sunset or with sun just over the treetops in the distant horizon, I have to resort to "Tungsten" preset shooting Raw or else the flower detail and folds of the petals blow out to ugly blobs no matter how much I try to adjust exposure.
In post I have to do further WB correction to get rid of the dull yellow film that seems to permeate throughout the image. There's something about the image that just doesn't look right if I don't correct for this.
Subsequently in doing so I have to boost saturation in the greens to give the impression a warm sun is shining on them. I also have to use a custom DNG camera profile that DOESN'T have a dual illuminant table. I tend to think my camera is just weird.
The sample below is such a saturated flower where I have to work separately on the flower as if it's a separate image from the rest and deal with the surround applying completely different edits.
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Where did I say that? In fact just the opposite. I’ve told you I use custom WB to season to taste. What I’m calling you on is your assertion that your subjective setting of WB is accurate. Hogwash I say. It is you that has the burden of proof that your preference for WB is accurate and in anyway correlates to the scene or can be measured. It is you that has the burden of proof that this process is anything but subjective.
Can you provide any scientific methodology to prove your use of WB is accurate and not subjective?
Setting white balance with the ACR white balance eyedropper is standard practice and is more accurate than an eyeball method, so I don't have to provide any scientific reference. Read your buddy's ACR book. In my case with the flower, I didn't take a white reading from my WhiBal, so I used a secondary standard of balancing on a white cloud taken under the same lighting conditions.
Regards,
Bill
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Setting white balance with the ACR white balance eyedropper is standard practice and is more accurate than an eyeball method, so I don't have to provide any scientific reference.
You don’t or you can’t? Pretty clear which is the case. Doesn’t matter. You continue to misuse and mangle a well defined word (accurate) despite my attempts, now you are telling us using a certain process in ACR is ‘standard practice’. I suppose you use that white bal card, click and never further adjust because that process produces perfect, accurate color?
No reason to continue, you clearly intend to make up your own facts.
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accuracy
n 1: the quality of nearness to the truth or the true value; "he
was beginning to doubt the accuracy of his compass";
"the lawyer questioned the truth of my account" [syn: truth]
[ant: inaccuracy]
* 2: (mathematics) the number of significant figures given in a
number; "the atomic clock enabled scientists to measure
time with much greater accuracy"
You don’t or you can’t? Pretty clear which is the case. Doesn’t matter. You continue to misuse and mangle a well defined word (accurate) despite my attempts, now you are telling us using a certain process in ACR is ‘standard practice’. I suppose you use that white bal card, click and never further adjust because that process produces perfect, accurate color?
If you understood the scientific definition of accuracy, you wouldn't have quoted a definition from a general dictionary. In science and statistics, accuracy and precision are strictly defined. See Wikipedia (http://en.wikipedia.org/wiki/Accuracy_and_precision) or a standard text. In Wikipedia, look at the target analogy. The number of decimal points has more to do with precision than accuracy.
In science and statistics, accuracy is the degree of closeness of measurements of a quantity to that quantity's actual (true) value. By doing as proper white balance, the appearance of the flower in the image is closer to what it was in the scene than if an inaccurate white balance had been used. Perfectly accurate color is not possible in current CFA sensors which do not follow the Luther-Ives conditions, but one strives to minimize the error. Use of eyeball white balance rather than measuring the white balance is absurd if one desires accuracy rather than a pleasing color for the flower. Pleasing can not be quantified, while color can (Delta E).
I agree there is no need to continue the discussion since you are not amenable to reason, as I have learned in previous discussions with you.
Regards,
Bill
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You change the WB as your first step in PP, but what is your white reference? If you were shooting in daylight, you could use daylight, but the color temperature of daylight varies through the day according to the position of the sun. According to measurements by a Kodak scientist (http://www.handprint.com/HP/WCL/color12.html), direct sunlight in the morning or afternoon has a CCT of 4300K whereas that at noon is 5400K. Daylight (a mixture of direct sun and skylight) is 6500K.
To illustrate, here is a shot of a flower taken at 9:37 a.m. on Sept 21 at a position of 42 N latitude using auto WB with the Nikon D3. The calculated zenith distance of the sun was 60 degrees. The camera looks at the actual colors in the image and not the color of the light. Since the image contains no neutral colors, the ACR WB is not accurate; ACR gives 4400K, which is renders the image as too blue.
(http://bjanes.smugmug.com/Photography/White-Balance/i-F55jQzf/0/L/019ACRAsShot-L.png)
Setting the color balance to daylight helps. ACR gives a WB of 5500K.
(http://bjanes.smugmug.com/Photography/White-Balance/i-Bg5LT2B/0/L/019ACRDaylight-L.png)
A more accurate WB can be taken from another image containing a white cloud as a reference point.
(http://bjanes.smugmug.com/Photography/White-Balance/i-D3tvXGw/0/L/027ACRCloudWB-L.png)
One can apply this WB setting to the flower image to obtain a more accurate rendering of the actual appearance of the flower.
(http://bjanes.smugmug.com/Photography/White-Balance/i-SP44wPn/0/L/019ACRCloudWB-L.png)
For accurate colors, it is usually best to take a WB reading from a neutral card such as a WhiBal. One could take several readings throughout day day when shooting at different times. One could set the WB to render the most pleasing colors, but if it is important to have accurate color, a WB reference point is necessary.
Regards,
Bill
This is all fine and well but I adjust white balance not to achieve a technically perfect white balance according to the precise time of day and/or position of the sun, but to my personal preference. I may want the scene to appear a bit warmer or cooler than it was in reality and I adjust white balance by "eyeing" it on my calibrated monitor. I'm not a scientist - I'm a photographer. An artist. As such, I take liberties with my art, one of which is setting a white balance that looks good to my eye.
Some times, I'll even blend two images set at different white balances to achieve a cooler temp in some parts of the image and a warmer temp in others. It boils down to personal preference, I guess.
One final point: Rarely do I ever use one of the white balance presets. I prefer to move the slider in Lightroom until the white balance looks good. I could care less what the number or setting is, so long as the final result is what I envision.
Good topic of conversation here, folks.
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Good topic of conversation here, folks.
Not for nothing but if you're gonna quote a post it would be useful to edit the quote to include the salient point (and not quote a post of multiple images).
There are a lot of ways to get your white balance optimal...it behooves you to know all of them including the use of the White Balance tool as well as manually adjusting the image visually.
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Pleasing can not be quantified, while color can (Delta E).
I believe that you can quantify subjective preferences and the impact of a given degradation by rounding up a representative group of people and doing a test. It is costly, time-consuming and prone to certain errors.
-h
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Setting white balance with the ACR white balance eyedropper is standard practice
Really? I think I can probably count on 2 hands the number of times I've used that method of adjusting WB in ACR or LR. OK, maybe two hands and 1 1/2 feet.
Your method of altering WB appears flawed. Applying the 5900K setting from another image has produced a very unpleasant colour cast and made the image too warm. Comparing the flower to the image you took the WB from, the reference image doesn't have nearly the warmth you've imparted to the flower shot.
Oh, by the way, you need to clean your lens or sensor or both. ::)
You calculate DeltaE values on all your images, do you?
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Really? I think I can probably count on 2 hands the number of times I've used that method of adjusting WB in ACR or LR. OK, maybe two hands and 1 1/2 feet.
So here’s an interesting reality check!
I shot a Passport under a Solux lamp. Measuring the illuminant with an EyeOne Pro I’m told the CCT value is 4176K. What does LR show for this value when the camera was set for Auto White Balance (As Shot)? 4100K (+7 for Tint). Not bad! Looks reasonable too.
What does the slider show after white balancing? 5001K with tint at +10. Too warm! And as some of you know, the Passport has a number of warm and cool white patches to use for seasoning to taste. Its quite possible to end up with something quite close to CCT 4100K (which I got simply by using Auto White Balance in the first place!).
Clicking on the same white patch in a different raw converter (Raw Developer), I get CCT 4232K.
OK Bill, which is accurate?
AWB looks great to me, the WB shot is too warm.
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which is accurate?
I can answer this beyond any shadow of a doubt!!!! YES is the correct answer! ;D
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Here's an example, Bill. The first image was shot with AWB and the As Shot WB in LR is 4450, Tint -16. A more 'accurate' white balance would have the wood more grey as in the second shot. The 'accurate' WB is 5180, Tint -5. While the second shot may be more 'accurate' it's definitely not as 'pleasing' as the first one - to me. I like the blue hue to the wood in the first shot. It's also more representative of the fact that the shot was taken in open shade.
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Very good example demonstrating this issue, Bob.
Now boost saturation on the first one that's pleasing but inaccurate to get back the warmth of the pinky peach hue to the right. That's what gets confused in applying WB is that our eyes want to see an optical white instead of the overall warm filter like look of the "accurate" one underneath.
Film often exaggerated this effect playing cool against warm except by amplifying it with saturation instead of R=G=B or accurate looking WB. Violet blue whites next to warm pastels makes for pleasing color but not necessarily accurate.
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And if this were a 'keeper' Tim, I'd do that additional kind of work on it. But this is just a throwaway.
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So here’s an interesting reality check!
I shot a Passport under a Solux lamp. Measuring the illuminant with an EyeOne Pro I’m told the CCT value is 4176K. What does LR show for this value when the camera was set for Auto White Balance (As Shot)? 4100K (+7 for Tint). Not bad! Looks reasonable too.
What does the slider show after white balancing? 5001K with tint at +10. Too warm! And as some of you know, the Passport has a number of warm and cool white patches to use for seasoning to taste. Its quite possible to end up with something quite close to CCT 4100K (which I got simply by using Auto White Balance in the first place!).
Clicking on the same white patch in a different raw converter (Raw Developer), I get CCT 4232K.
OK Bill, which is accurate?
AWB looks great to me, the WB shot is too warm.
I can't really determine which is more accurate merely from a screen shot re-displayed on my screen. Your custom WB with a temp of 5000K and a tint of +10 sounds a bit screwy. Rather than eyeballing the images, one should use an objective measurement. I took pictures of a ColorChecker with my D3, illuminated by 6 Solux bulbs. I rendered into sRGB with ACR using the AdobeStandard profile. Since the color checker contains a wide range of colors and neutrals, I expected auto WB to perform well, and it did.
Here is the As Shot image. It is the real image, not a screen shot. The Temperature reads 4000 and the Tint -11. The whites and grays are slightly off.
(http://bjanes.smugmug.com/Photography/White-Balance/i-Q3kxwv8/0/O/Img0005AsShot.jpg)
Here is the custom WB image, white balanced in ACR with the WB eyedropper on gray patch two. The Temp was 3900 with a Tint of -1. The neutral patches are more neutral.
(http://bjanes.smugmug.com/Photography/White-Balance/i-4z6cMbz/0/O/Img0005Custom.jpg)
One can check for accuracy with Imatest. The results are shown. The custom white balance shows better overall accuracy by a small margin. Note especially that the Delta C for the middle neutral patches is much better with the custom WB.
As shot WB:
(http://bjanes.smugmug.com/Photography/White-Balance/i-HbpQJrn/0/O/Img0005AsShotexpMinuscolorerro.png)
Custom WB:
(http://bjanes.smugmug.com/Photography/White-Balance/i-cPFLNmG/0/O/Img0005CustomexpMinuscolorerro.png)
However, auto WB does not work well when the image contains a dominant strong color and no neutrals, as in my original flower shot. To simulate this condition, I took a close up of the color checker such that the frame was largely filled by the red patch. The black surrounding the patches constitutes a small amount of neutral. The As Shot WB as read by ACR was 3450 with a tint of -23. The color was way off as expected.
(http://bjanes.smugmug.com/Photography/White-Balance/i-rtxvknf/0/O/DSC49830008.jpg)
Here is the proper custom WB from the full shot of the checker with the erroneous Auto WB from the close up shown as in inset.
(http://bjanes.smugmug.com/Photography/White-Balance/i-4g6TBpD/0/O/Img0005CustomComp.jpg)
QED.
Regards,
Bill
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Bill, you're missing the entire point that people are trying to convey. Either that or you're just ignoring it on purpose. "Accurate" isn't always "best".
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Really? I think I can probably count on 2 hands the number of times I've used that method of adjusting WB in ACR or LR. OK, maybe two hands and 1 1/2 feet.
The number of times you have used the white balance tool does not concern me, since I have no way to evaluate your level of experience and technical proficiency. As Guillermo pointed out (post 32) the intent of white balancing varies. Sometimes technical accuracy is needed, while in other cases an artistic impression is required. What is your intent? If one were to conduct a survey of Micheal Tapes' (WhiBal) customers, the number of users using the white balance tool would be much higher than in your case. :)
Your method of altering WB appears flawed. Applying the 5900K setting from another image has produced a very unpleasant colour cast and made the image too warm. Comparing the flower to the image you took the WB from, the reference image doesn't have nearly the warmth you've imparted to the flower shot.
Really? As I stated in my post, my aim in the WB was for technical accuracy and not for artistic intent. Your subjective evaluations are not relevant, since you have no way to relate the color in the image to that in the scene. The white balance would ideally be accomplished by reading of a neutral in the scene, but no definite neutral is present. The best that can be done is to use the white balance from another scene that does include a neutral, in this a white cloud. See my reply to DigitalDog where auto white balance on a close up of the ColorChecker red patch was way off. By using the WB from a different image containing the entire chart, accurate WB can be obtained and the color of the red patch is much more accurate than with auto WB.
You calculate DeltaE values on all your images, do you?
Obviously not, but I do calculate DeltaE when calibrating my camera. DeltaE can not be calculated from most routine images, since reference colors are not available. I don't carry a spectrophotometer in the field, nor do most users, and your comment is gratutious. DeltaE includes luminance, hue, and chroma. DeltaC as shown in the Imatest color checker plots removes the luminance component. Further, an increase in chroma (saturation) is often desired, but shifts in hue are not. A faulty WB can produce hue shifts. The informed photographer is aware of such considerations. Are you?
Regards,
Bill
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Bill, you're missing the entire point that people are trying to convey. Either that or you're just ignoring it on purpose. "Accurate" isn't always "best".
Please refer to Guillermo's post 32. If you want to reproduce the color of a red Ferrari for a car brochure, accurate is best. The same applies to catalog reproductions of merchandise where the color of a garment must be accurately shown. The same applies to scientific work. If an artistic effect is desired, then by all means adjust the WB. Even here, an technically correct WB is often a good starting point. It is you who can't or won't read what I was saying regarding my intent for WB.
Regards,
Bill
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Please refer to Guillermo's post 32. If you want to reproduce the color of a red Ferrari for a car brochure, accurate is best.
You’re confusing (again) ‘accurate’ with a color match. The numbers could (most likely will) be totally different from the measured (spectral to lab to RGB values) of the Ferrari and that which you end up with visually matching in on output referred device.
I can't really determine which is more accurate merely from a screen shot re-displayed on my screen.
Then there is something seriously wrong with your display! The WB image is way too warm while the AWB is pretty much a spot on visual match.
Bill, you're missing the entire point that people are trying to convey. Either that or you're just ignoring it on purpose. "Accurate" isn't always "best".
Worse, he’s making up a term (accurate) without any way to backup what that means, when its invoked, and how its calculated. If it looks right, its “accurate”. Why not just say, it looks right?
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Then there is something seriously wrong with your display! The WB image is way too warm while the AWB is pretty much a spot on visual match. At first, I couldn't believe that his neutral values could be off that much and was looking for an explanation. Apparently faulty technique.
There's nothing wrong with my display. See the calibration results. However, rather than posting a screen shot, it would be much better to post the actual photo.
(http://bjanes.smugmug.com/Photography/White-Balance/i-ZL7P2th/0/O/SynchmasterCalib.png)
There is something seriously wrong with your white balance. If you used the WB dropper, the RBG values in the neutral patches should be equal, while in fact they are far from equal. You should repeat your experiment.
(http://bjanes.smugmug.com/Photography/White-Balance/i-NBBWBRh/0/O/DigiDog.png)
Worse, he’s making up a term (accurate) without any way to backup what that means, when its invoked, and how its calculated. If it looks right, its “accurate”. Why not just say, it looks right?
Accurate (scientific definition from Wikipedia (http://en.wikipedia.org/wiki/Accuracy_and_precision)): "In the fields of science, engineering, industry and statistics, the accuracy[1] of a measurement system is the degree of closeness of measurements of a quantity to that quantity's actual (true) value."
The accuracy of a color measurement can be expressed as DeltaE or DeltaC as shown in my Imatest examples. Without any reference points an image that looks right could be far from the actual color values in the image.
This is not my first exchange with the DigitalDog. See "Does a raw file have a color space? (http://en.wikipedia.org/wiki/Accuracy_and_precision)". In that exchange he refuses to reply to logic, throws in red herrings, changes the topic, does not remain on task, and even declines to listen to the opinions of his own experts (Thomas Knoll and others).
What about the auto WB in the close up of the red patch? Is that accurate? Does it look right? One could compare the rendered color to the actual color of the patch and calculate a DeltaC.
I give up with the DigitalDog. This emperor has no clothes!
Regards,
Bill
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There is something seriously wrong with your white balance. If you used the WB dropper, the RBG values in the neutral patches should be equal, while in fact they are far from equal. You should repeat your experiment.
Nope. Not so. As you can see, I clicked on a white patch! In fact, the RGB values change based on which white I WB on. Some more than others. Now if you were looking closely, you’d see I WB on the first white patch of the Macbeth. The 2nd is a better move. The difference in the rendering is far from subtle. Yet WB I did. BUT, in your own examples here, you WB on a cloud to produce an “accurate” WB (again, this is nonsense description). Since you seem to feel one can WB on any white, neutral or not, you will see as I did in this example, WB is not ‘accurate’ and which white you WB plays a big role in getting a preferred (pleasing) rendering. The white patch as measured in that Passport IS neutral. And yet, WB on that one patch, the result is a warm rendering which is not ‘accurate’ but more important, not pleasing to me as the image creator looking at the scene and the capture on my display. Had I shot this under candlelight, I may have preferred this warm rendering. If I wished to express the image shot under Solux as candlelight, this image would be fine.
WB is subjective. Why do you suppose a company like X-Rite put a range of white’s with warmth and coolness into the Passport? Accuracy is term that doesn’t belong in the conversation. That’s the bottom line. Your use of the term ‘accurate’ is misleading. As I said here, you may say you WB and its accurate and I can disagree. You can say its close, I can say its closer or not closer and its all subjective. You’ve as yet supplied no methodology of measuring scene colorimetry and providing any proof that its accurate to the output referred data you end up with. It matches what you believe is the original, great. Calling that accurate instead of describing this as subjective with no way to back up an accuracy metric should be dismissed.
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No, Bill. I have read what you've written. I simply reject the premise for the most part.
As I stated in an earlier comment (which you may not have read) there are times when an 'accurate' white balance is desired. And some of the instances you mentioned are examples. But I reject the premise that simply correcting WB to the same temperature as the lighting source will render the colours as most 'accurate' in the image in every situation. Might in some, but not in others. I do some copy work for artists. I use an XRite Passport as a tool to try and make sure my starting point is as close as it can be. But inevitably I end up adjusting from that starting point because the colours in the image may still not be 'accurate' even after adjusting to the 'proper' white balance. That won't absolutely get you a colour match between the original object and the end image. It simply won't. I agree that 'accuracy' (i.e., a match) in colour reproduction is important in the instances noted. I reject the idea that WB is the only or single way to achieve that.
In the image you keep coming back to of taking a WB reading off one image to apply it to another, I'll continue to say that methodology is flawed. The lighting in that scene with the clouds is very different from the lighting you end up with in the flower image. You like it, fine. I think it's far too warm and unless you measured the colours of the flower there's absolutely no way you can tell me with any degree of certainty that the colours in the flower are 100% 'accurate'. My bet is they're not.
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From what I've seen from Andrew's posted WB test image compared to Bjane's is that camera's clearly have different quality and characteristic filtering (infrared?) systems that influence how a Raw converter finally interprets the appearance of each camera's AutoWB under any given light source.
Bjanes makes valid points about that. His camera's AutoWB sees the Solux lit neutrals as too red and so bumps up the green while Andrews sees it (assumptions based on observation) as too bluegreen and bumps up yellow orange/amber.
It's not been mentioned that image reproduction is nothing but a magic trick that fools the optics of human vision into seeing something that resembles reality which has certain emotional aspects that induce us to trip the shutter.
It's much like ventriloquism tricks the human auditory system by having the ventriloquist attenuate certain directional audio frequencies humans use to determine source and direction of a particular sound. (Capital Record's audio engineers put this knowledge to good use in coming up with their famous stereo imaged "echo chamber"). Measuring these mimicked frequencies with a machine won't necessarily deliver identical wave pattern formations but the actual sound was enough to fool the listener's ear due to their position to the ventriloquist.
A spectrophotometer only reads energy waves of light and assigns a number no matter what type of light source. There's no attempt or consideration in attenuating these spectral frequencies into fooling the eye. This is what Andrew refers to as "scene referred". It's accurate according to a spectrophotometer but it doesn't take into consideration human optic's persistent adapting to the surround effect of that scene that a spectrophotometer has no clue about.
So when we capture "scene referred" color that may be "accurate" according to a machine, when we view this out of its surround that our eyes adjusted for at the time we tripped the shutter and now view in our dark warm lit studio, the "accurate" color looks butt ugly on our calibrated display which makes it even more uglier from the display's attempt at artificially mimicking D65/6500K daylight.
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But I reject the premise that simply correcting WB to the same temperature as the lighting source will render the colours as most 'accurate' in the image in every situation. Might in some, but not in others. I do some copy work for artists. I use an XRite Passport as a tool to try and make sure my starting point is as close as it can be. But inevitably I end up adjusting from that starting point because the colours in the image may still not be 'accurate' even after adjusting to the 'proper' white balance. That won't absolutely get you a colour match between the original object and the end image. It simply won't. I agree that 'accuracy' (i.e., a match) in colour reproduction is important in the instances noted. I reject the idea that WB is the only or single way to achieve that.
I agree that simply setting the white point will not ensure an accurate reproduction of the image. However, it is a first start. I use the DNG profile editor to create a custom profile for my camera which improves the color accuracy as measured by Imatest ColorChecker. However, to get the most accurate results, I need to use a linear tone curve in ACR, and readily concur that a linear tone curve does not produce pleasing results.
In the image you keep coming back to of taking a WB reading off one image to apply it to another, I'll continue to say that methodology is flawed. The lighting in that scene with the clouds is very different from the lighting you end up with in the flower image. You like it, fine. I think it's far too warm and unless you measured the colours of the flower there's absolutely no way you can tell me with any degree of certainty that the colours in the flower are 100% 'accurate'. My bet is they're not.
Of course, the colors are not 100% accurate. Use of a custom profile helps, but since the CFA filters of any camera do not meet the Luther-Ives criteria, metameric error will occur and it can only be minimized by a profile. I agree that the use of a cloud is not the best way to measure white balance. However, my point was that if the image contains a predominant saturated color and no neutrals, automatic color balance will be thrown off. This was demonstrated with a close up of the red patch of the color checker and AutoWB. In this situatiion one can take the WB from another shot under identical conditions or even better, take a custom WB from a neutral target. With no accurate WB, you could adjust the image to produce a pleasing result, but without a reference point, you would have to rely on memory to get the color right. Color memory is not very reproducible.
I haven't done museum reproduction work, but I understand that the best results are obtained with a multishot back using apochromatic lenses and a custom ICC profile, perhaps in Capture One. What is your experience?
Regards,
Bill
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It's much like ventriloquism tricks the human auditory system by having the ventriloquist attenuate certain directional audio frequencies humans use to determine source and direction of a particular sound. (Capital Record's audio engineers put this knowledge to good use in coming up with their famous stereo imaged "echo chamber"). Measuring these mimicked frequencies with a machine won't necessarily deliver identical wave pattern formations but the actual sound was enough to fool the listener's ear due to their position to the ventriloquist.
A spectrophotometer only reads energy waves of light and assigns a number no matter what type of light source. There's no attempt or consideration in attenuating these spectral frequencies into fooling the eye. This is what Andrew refers to as "scene referred". It's accurate according to a spectrophotometer but it doesn't take into consideration human optic's persistent adapting to the surround effect of that scene that a spectrophotometer has no clue about.
So when we capture "scene referred" color that may be "accurate" according to a machine, when we view this out of its surround that our eyes adjusted for at the time we tripped the shutter and now view in our dark warm lit studio, the "accurate" color looks butt ugly on our calibrated display which makes it even more uglier from the display's attempt at artificially mimicking D65/6500K daylight.
Good points, but AFAIK, all color reproduction must take chromatic adaption into account. The CIE standard observer assumes complete chromatic adaption.
Regards,
Bill
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So when we capture "scene referred" color that may be "accurate" according to a machine, when we view this out of its surround that our eyes adjusted for at the time we tripped the shutter and now view in our dark warm lit studio, the "accurate" color looks butt ugly on our calibrated display which makes it even more uglier from the display's attempt at artificially mimicking D65/6500K daylight.
Exactly. So the correct term here, accurate (colorimetrically correct) makes a butt ugly reproduction, inaccurate values produce a visual match. The later has values which one may be able to use to produce some kind of deltaE report that shows huge ‘errors’ yet the result is what we desire, a visual match. That is also subjective.
And when we use metrics like dE, we are examining a single solid color patch or a group of them. Even if we make a report with thousands of such colors, those are not the same as viewing an image in context. If you want to measure a spot color off the Ferrari, even a few dozen, fine. You could report an accurate or inaccurate colorimetric match (which probably doesn’t visually match on the output referred media).
All this talk of accuracy is silly with imagery which is far too complex to analyze in such simplistic terms. Just look at Bill’s evidence that his display is accurate. A few colors (selected by the software itself), which is supposed to define the accuracy of its entire color space. And using the same instrument. Not worthless but not very telling. This is all fine if you are asking about the accuracy of color patches measured and then output to these solid patches (deltaE of the profile as an example). Or the consistency of a device over time. Using the same process to define the accuracy of a image when you can simply look at it and say “it matches” is enough. That analysis is subjective. So again, using the term accuracy here when what we are expecting is a color match of a complex image is counterproductive and disingenuous.
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Good points, but AFAIK, all color reproduction must take chromatic adaption into account. The CIE standard observer assumes complete chromatic adaption.
You left out one major factor that's not included in the CIE standard observer, emotions and memory in relation to what was seen in the actual scene and how it's perceived on an artificial viewing environment that is a darkened studio and LCD CCFL/LED backlit display. With these variables makes nailing it by the numbers and having it look as intended about as impossible as predicting the weather.
Ballpark is the best that can be done. That's what I've found making a custom DNG camera profile with a Color Checker Chart which doesn't have enough sample colors to compensate for all possible scenes captured with WB appearance being the least of concerns which the profile is forced to dovetail into because of optical effects on human perception not factored in by a machine or any color description standards or encoding.
It was what I was pointing out in Bob's sample image where saturation levels play tricks with cool/warm relationships that has to be judged by the overall look of the image and not by each color by the numbers.
I figured from this optical effect as the reason why my X-rite i1Display calibration software doesn't induce/correct for chromatic adaptation in the matrix transforms of the profile that control hue/saturation very well when I choose a 5000K white point appearance on my display.
In color managed apps using this profile loaded in the system colors affected by this change to WB appearance aren't corrected for as they would appear on a print under the same color temp light. An error in technology? Or is the software written/tuned to write the matrices of the profile expecting 6500K white?
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Below is an example from my experimenting with the way different "flavors"=(spectral reflectance qualities imbued to an image) of two types of light that bring their own color palette to the overall look of an image in creating an optical effect that can't be corrected with WB adjustments whether in front or behind the camera. "Tungsten" WB preset was used incamera for the one on the left and "Fluorescent White Light" on the right of the Alzo rated at 5500K.
Note the brown color of the hand lit by a hot light on the left compared to the greenish patina of the hand on the right. I can't make the one on the right have the same hue of brown on the left no matter what I do WB editing the Raw images in ACR. Notice the one on the right has R=G=B neutral background but it looks blue. This "undercolor" or "patena" effect has been used by Dutch Master painters using paint on canvas long before Kodak engineers got into the act of image reproduction. This optical effect also can't be factored in by CIE Standards for determining how accuracy should look according to WB appearance.
Even if you could get the color patches I sampled from the skin tones to match exactly by the numbers included in the corners, the overall appearance between the images would be even farther apart because machines can't over ride this optical effect.
Whether you light the scene with the sun, flashlight, living room light, Alien Bees strobes, you name it, each light will imbue the image with their own undercolor with some offering their own color palette that's more or less noticeable in varying degrees depending on the subject and the light lit by it.
I exaggerated this effect by editing both images to bring out this undercolor optical effect influenced by various light sources.
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I agree that simply setting the white point will not ensure an accurate reproduction of the image. However, it is a first start.
That's not really what you've been intimating up till now. You've been saying that getting the WB 'accurate' will result in 'accurate' colour reproduction in the scene. If it's nothing more than a 'first start' then it's really no better than any other method.
I use the DNG profile editor to create a custom profile for my camera which improves the color accuracy
Don't necessarily disagree with that. I've got a Passport as well and use it for the same purpose. But even then I may still have to tweak the colour to get it to be as close a match as possible.
Of course, the colors are not 100% accurate. Use of a custom profile helps, but since the CFA filters of any camera do not meet the Luther-Ives criteria, metameric error will occur and it can only be minimized by a profile. I agree that the use of a cloud is not the best way to measure white balance. However, my point was that if the image contains a predominant saturated color and no neutrals, automatic color balance will be thrown off. This was demonstrated with a close up of the red patch of the color checker and AutoWB. In this situatiion one can take the WB from another shot under identical conditions or even better, take a custom WB from a neutral target. With no accurate WB, you could adjust the image to produce a pleasing result, but without a reference point, you would have to rely on memory to get the color right. Color memory is not very reproducible.
Well, at least you've admitted that your method isn't 100% 'accurate'. That's a start. And if I need to match colours as closely as possible then I'm not going to work from memory either. Nor do I think Andrew or Tim or a lot of others would. The difference is in the recognition that what you're calling 'accurate' may not end up being a 'match' in the final image.
I haven't done museum reproduction work, but I understand that the best results are obtained with a multishot back using apochromatic lenses and a custom ICC profile, perhaps in Capture One. What is your experience?
Sorry, where did I say I was doing museum reproduction? As far as equipment, The Tate in London uses, I believe, Hasselblad with both single and multi-shot backs. I don't know what RAW converter they use but suggesting C1 is the best is like saying LR is the best or DxO. What's best for one may not be for another. While something like the Hassy H4D-200MS is a terrific system, I can't justify the $45k cost (before lenses). So I make due with a less 'accurate', single shot, full frame DSLR and the best lenses I can afford. Still a pretty darn good system and far better than the compacts or low end DSLR/kit lens options many artists use if they do their own reproduction work.
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Random question: blue skies are often more "purple-ish" when I view them directly with my eyes, and more "blue-ish" when I view them while wearing sunglasses. Definitely a different hue. Which is more accurate?
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Nope. Not so. As you can see, I clicked on a white patch! In fact, the RGB values change based on which white I WB on. Some more than others. Now if you were looking closely, you’d see I WB on the first white patch of the Macbeth. The 2nd is a better move. The difference in the rendering is far from subtle. Yet WB I did. BUT, in your own examples here, you WB on a cloud to produce an “accurate” WB (again, this is nonsense description). Since you seem to feel one can WB on any white, neutral or not, you will see as I did in this example, WB is not ‘accurate’ and which white you WB plays a big role in getting a preferred (pleasing) rendering. The white patch as measured in that Passport IS neutral. And yet, WB on that one patch, the result is a warm rendering which is not ‘accurate’ but more important, not pleasing to me as the image creator looking at the scene and the capture on my display. Had I shot this under candlelight, I may have preferred this warm rendering. If I wished to express the image shot under Solux as candlelight, this image would be fine.
As I said before, there is something seriously wrong with your white balance in that shot, when you get a WB of 5100K with a tint of +10 when the correct WB would be around 4100K. You used the white patch, which is inadvisable since that patch is not spectrally neutral. It is difficult to make spectrally neutral paint with that high of a reflectance. The average values for the neutral patches in sRGB values are shown below as determined by Bruce Lindbloom.
(http://bjanes.smugmug.com/Photography/White-Balance/i-k3RCnWV/0/O/ColorCheckersRGBb.png)
Another reason for not using the white patch is to avoid clipping of channels, but ACR won't allow a WB with clipped channels. Patch 2 is usually recommended since it is unlikely to be clipped and the signal to noise is high in this patch. However, if your camera has a good S:N, any of the patches 2-6 can be used with good results. An 18% spectrally neutral card is fine with the D3. Here is the WB I got for the D3 with neutral patches 1 through 7. However, the error induced by reading from the white patch is minimal, and I suspect that your camera has serious nonlinearity. However, you could check the WB by determining if the RBG values are equal in the mid patches. I requested this information, but you did not respond and implied that there must be something seriously wrong with my display. The readings I posted show that they were not equal in your screen shot when viewed in Photoshop and assigning the sRGB to the download of your image. I presume that the color numbers in a screen shot would be for your monitor profile and you then converted to sRGB for viewing on the internet. The actual screen colors would vary with the white point of the monitor and its color response.
(http://bjanes.smugmug.com/Photography/White-Balance/i-zt49x4V/0/S/MacBethWB-S.png)
WB is subjective. Why do you suppose a company like X-Rite put a range of white’s with warmth and coolness into the Passport? Accuracy is term that doesn’t belong in the conversation. That’s the bottom line. Your use of the term ‘accurate’ is misleading. As I said here, you may say you WB and its accurate and I can disagree. You can say its close, I can say its closer or not closer and its all subjective. You’ve as yet supplied no methodology of measuring scene colorimetry and providing any proof that its accurate to the output referred data you end up with. It matches what you believe is the original, great. Calling that accurate instead of describing this as subjective with no way to back up an accuracy metric should be dismissed.
I would submit that WB is not subjective. If your camera had a sensor fully compliant with the Luther-Ives criteria, you would get accurate colors only if you used the proper white balance. Of course, no camera sensor is Luther-Ives compliant, but you will likely get the most accurate color reproduction when using the true WB and a good camera profile. If you want pleasing colors, then feel free to tweak the image to your heart's content. The tinted patches on the Passport are not to obtain an accurate white balance, but to change the WB to produce an artistic rendering. If you wanted the image to be warmer, you could use merely use a neutral patch and then alter the WB temperature to achieve the same effect.
With the flower, obviously I do not have colorimetry. However, I did present data using the Color Checker with well defined patches and demonstrated that auto WB was reasonably with my camera accurate when it is determined from the entire color checker, but is seriously deficient with a close up of the red patch, and I presented quantitative data with DeltaE and DeltaC. Thus far, all that you have presented is a faulty WB and a screen capture showing undefined colors.
Regards,
Bill
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That's not really what you've been intimating up till now. You've been saying that getting the WB 'accurate' will result in 'accurate' colour reproduction in the scene. If it's nothing more than a 'first start' then it's really no better than any other method.
The purpose of my post was that an accurate WB will give more accurate colors than would be obtained with a poor WB. The colors may have to be tweaked, but I think that it is a better start than would be obtained with an inaccurate WB. The flower in my shot had no neutral colors and the auto WB was off. I should have used my WhiBal, but could have set the WB to daylight in ACR and obtained reasonable results. I merely chose the image from what I had available from a recent shoot to demonstrate a point: auto WB is not good when the scene contains no neutrals and a predominant strongly saturated color. Adjusting the WB to produce a match was not possible since I no longer had the flower in front of me and my recollection of the color would likely be faulty.
Sorry, where did I say I was doing museum reproduction? As far as equipment, The Tate in London uses, I believe, Hasselblad with both single and multi-shot backs. I don't know what RAW converter they use but suggesting C1 is the best is like saying LR is the best or DxO. What's best for one may not be for another. While something like the Hassy H4D-200MS is a terrific system, I can't justify the $45k cost (before lenses). So I make due with a less 'accurate', single shot, full frame DSLR and the best lenses I can afford. Still a pretty darn good system and far better than the compacts or low end DSLR/kit lens options many artists use if they do their own reproduction work.
Where did I say you were doing museum reproduction? And where did I say that C1 would be the best raw converter? I don't do museum reproduction, but I understand that the best results might be obtained with a full ICC camera profile under standardized conditions and suggested that C1 would be a possible raw converter, since it allows use of ICC camera profiles. ACR with a DNG profile from a color checker would be a reasonable alternative, but more patches are needed for a more comprehensive profile.
Regards,
Bill
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As I said before, there is something seriously wrong with your white balance in that shot, when you get a WB of 5100K with a tint of +10 when the correct WB would be around 4100K.
You want the DNG to see for yourself? Ask yourself how this is ‘wrong’. You see in the screen grab the WB tool after clicking on the white patch, you see the results of the WB values. So what’s seriously wrong? Well for one, its not ‘accurate’? Not necessary to use such language, I can SEE its too warm, the point of my first post correcting your language!
You used the white patch, which is inadvisable since that patch is not spectrally neutral.
Like your clouds? So now your take is, WB is ‘accurate’ but you have to click on something spectrally neutral? So you’re updating your story now?
Patch 2 is usually recommended since it is unlikely to be clipped and the signal to noise is high in this patch.
Your preaching to the choir. I said this already.
However, if your camera has a good S:N, any of the patches 2-6 can be used with good results. An 18% spectrally neutral card is fine with the D3. Here is the WB I got for the D3 with neutral patches 1 through 7. However, the error induced by reading from the white patch is minimal, and I suspect that your camera has serious nonlinearity. However, you could check the WB by determining if the RBG values are equal in the mid patches. I requested this information, but you did not respond and implied that there must be something seriously wrong with my display. The readings I posted show that they were not equal in your screen shot when viewed in Photoshop and assigning the sRGB to the download of your image. I presume that the color numbers in a screen shot would be for your monitor profile and you then converted to sRGB for viewing on the internet. The actual screen colors would vary with the white point of the monitor and its color response.
Bla, bla, bla.... The point of the illustration was to point holes in your “WB is accurate” nonsense, no reason to respond about your display or other readings. WB is subjective, you still don’t seem to get that. Even if I WB on the 2nd patch, I may or may not like the rendering. It may or may not better visually match the scene! And you see to believe that all illuminants when set for a neutral WB are ‘accurate’ let alone produce a desired subjective rendering which is just silly talk.
I would submit that WB is not subjective.
You clearly have, while no one as yet agrees with you, probably based on all the reasons expressed in this long set of posts. Accurate how, based on colorimetry of the scene? If you can’t provide such a metric, how can you say its accurate? Seems like a totally subjective statement since you have nothing else to back up the science.
If your camera had a sensor fully compliant with the Luther-Ives criteria, you would get accurate colors only if you used the proper white balance.
And if my aunt was a man, she'd be my uncle. Stay on track if you are going to ignore your own advise and give up. Tell us how the values are colorimetrically accurate.
With the flower, obviously I do not have colorimetry.
Yet you continue to believe and preach its accurate color. So its accurate or its not? Either way, you are using what process to define accuracy?
However, I did present data using the Color Checker with well defined patches and demonstrated that auto WB was reasonably with my camera accurate when it is determined from the entire color checker, but is seriously deficient with a close up of the red patch, and I presented quantitative data with DeltaE and DeltaC.
What you illustrated is with your camera system, you can hose the WB assumption, nothing more. Reasonably close? You came up with that metric how? Its difficult to take you seriously with such language.
Thus far, all that you have presented is a faulty WB and a screen capture showing undefined colors.
Yes! Exactly doing what you yourself said would produce accurate color. That’s exactly why I posted it!
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The purpose of my post was that an accurate WB will give more accurate colors than would be obtained with a poor WB.
Ah, so if I shoot a spectrally neutral white patch while shooting a girl on the beach at sunset, then WB on it, its more accurate?
Same question, this time the scene is shot under candlelight. Or in an early morning fog bank.
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The purpose of my post was that an accurate WB will give more accurate colors than would be obtained with a poor WB. The colors may have to be tweaked, but I think that it is a better start than would be obtained with an inaccurate WB. The flower in my shot had no neutral colors and the auto WB was off. I should have used my WhiBal, but could have set the WB to daylight in ACR and obtained reasonable results. I merely chose the image from what I had available from a recent shoot to demonstrate a point: auto WB is not good when the scene contains no neutrals and a predominant strongly saturated color. Adjusting the WB to produce a match was not possible since I no longer had the flower in front of me and my recollection of the color would likely be faulty.
I don't know about anybody else, but I'm getting dizzy going around in these circles. The bottom line is that your method isn't 'accurate' it's just a different starting point. Nothing more.
Where did I say you were doing museum reproduction? And where did I say that C1 would be the best raw converter? I don't do museum reproduction, but I understand that the best results might be obtained with a full ICC camera profile under standardized conditions and suggested that C1 would be a possible raw converter, since it allows use of ICC camera profiles. ACR with a DNG profile from a color checker would be a reasonable alternative, but more patches are needed for a more comprehensive profile.
You said your impression was that a multishot back with APO lenses was the best tool for the job in museum reproduction and that that it might be even better using ICC profiles in C1 then asked what my experience was. That, to me, seems to be asking what my experience is in doing museum reproduction. Do even read what you write? I think other RAW converters can work with ICC profiles as well. I believe Hassy's own Phocus software can. ICC profiles necessary? Better than a DNG profile? Debatable. But let's get back to the issue. Do you know why multishot backs are suggested as the ultimate option? How many shots? The Hassy does, I think, 6. There are others that do 16. Why the extra 10? Oh never mind. It was a red herring argument to begin with and it didn't catch me out as you probably thought it might so let's just drop it, shall we.
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You want the DNG to see for yourself? Ask yourself how this is ‘wrong’. You see in the screen grab the WB tool after clicking on the white patch, you see the results of the WB values. So what’s seriously wrong? Well for one, its not ‘accurate’? Not necessary to use such language, I can SEE its too warm, the point of my first post correcting your language!
Like your clouds? So now your take is, WB is ‘accurate’ but you have to click on something spectrally neutral? So you’re updating your story now?
Yes, I would like to have the DNG. Can you upload it to your web site and provide a link? You say the rendering is too warm, but are the neutrals neutral? Do the color patches have the proper RGB values? If so, I would say that your capture is accurate. If you think that it is too warm and make your correction to produce a pleasing result and the color values vary from what they should be, I would say that your reproduction is inaccurate, even though you may find it pleasing. From you screen shot I can't determine what any of the values in the capture are, since the meaning of the RGB values in that capture are not defined.
My use of clouds for WB is not optimal, but of the images in that shoot, the clouds were the best reference point that was available. If I had used a WhiBal target positioned next to the flower, you likely would still insist on some adjustment to produce color pleasing to you. A color match to the flower would rely on memory and would be entirely subjective.
Bla, bla, bla.... The point of the illustration was to point holes in your “WB is accurate” nonsense, no reason to respond about your display or other readings. WB is subjective, you still don’t seem to get that. Even if I WB on the 2nd patch, I may or may not like the rendering. It may or may not better visually match the scene! And you see to believe that all illuminants when set for a neutral WB are ‘accurate’ let alone produce a desired subjective rendering which is just silly talk.
Yes! Exactly doing what you yourself said would produce accurate color. That’s exactly why I posted it!
You may or may not like the rendering, but do the colors of the patches in your image match those on the color checker? If so, I would say that your rendering is accurate. Your perception of the scene is irrelevant--for all I know you could have been on LSD and hallucinating. One can measure color stimuli, but not perception. Nowhere did I state that an accurate WB would produce the desired subjective rendering. I want my rendering into a defined color space with a defined white point, and I will go from there to produce the intended result. Your improper WB produced improper colors and proved nothing. Post the DNG and I will analyze the colors with Imatest and see how accurate they are.
An accurate capture of the color checker accurately printed on a paper surface similar to that of the color checker would reproduce the target and it would not matter what the viewing conditions were (assuming that the paper didn't exhibit metameric failure like the first Epson pigment device.
As to the sunset scene or a candlelit scene, WB will not produce the perceived scene colors, since the eye does not chromatically adapt to such red colors. At more reasonable temperatures of 3200-6000K, adaption does occur and WB reproduces the perceived colors.
Regards,
Bill
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Yes, I would like to have the DNG. Can you upload it to your web site and provide a link?
I’ll put it on my public iDisk**.
You say the rendering is too warm, but are the neutrals neutral?
Nope.
Do the color patches have the proper RGB values?
Now what would be proper? Its been handled in LR. Proper would be MelissaRGB using percentage values. And no, the values are probably not proper considering the color appearance doesn’t look anything like the scene (its too warm, as stated).
If so, I would say that your capture is accurate.
Your kidding with that question right?
If you think that it is to warm and make your correction to produce a pleasing result and the color values vary from what they should be, I would say that your reproduction is inaccurate, even though you may find it pleasing.
Its neither pleasing or a good reproduction of the scene BECAUSE of the CURRENT WB. That’s the point! I’m not sure you are reading and understanding what I and others have written (I’m not the first person to suggest this).
From you screen shot I can't determine what any of the values in the capture are, since the meaning of the RGB values in that capture are not defined.
It doesn’t matter what the current values are! They can be changed any number of ways.
My use of clouds for WB is not optimal, but of the images in that shoot, the clouds were the best reference point that was available.
And according to you accurate. That is what originally raised the hairs on my neck. Your process and more critically, your language!
If I had used a WhiBal target positioned next to the flower, you likely would still insist on some adjustment to produce color pleasing to you. A color match to the flower would rely on memory and would be entirely subjective.
Yet WB isn’t subjective? You are a difficult fellow to understand.
You may or may not like the rendering, but do the colors of the patches in your image match those on the color checker?
No, I’d need to gather scene referred colorimetry and the data in LR is output referred. Apples and oranges. I’d need data about the specific illuminant (because just measuring the colors with the i1Pro, its resulting RGB values don’t take this into account, its got its own light source).
If so, I would say that your rendering is accurate.
I bet you would. But that would be a really big and unproven assumption, the root of our disagreement.
Your perception of the scene is irrelevant--for all I know you could have been on LSD and hallucinating.
After all these posts, I wish. But since my sense of the scene is my perception, maybe you’ll tell us how you’d get past this to label it accurate otherwise? I’ve been asking for an accuracy metric and technique for days now.
Nowhere did I state that an accurate WB would produce the desired subjective rendering.
Its accurate Colorimetrically? You go about this how?
I want my rendering into a defined color space with a defined white point, and I will go from there to produce the intended result.
And this relates to the actual scene colorimetry how, and how do you correlate and calculate the accuracy from scene to this color space? That would go a long way to understanding your use of the term ‘accurate’. And on the same topic, after you’ve told us how you come to this calculation, what’s the metric for less than and inaccurate?
Post the DNG and I will analyze the colors with Imatest and see how accurate they are.
Which will tell us what about the scene colorimetry? If you alter any of the settings in a raw converter, then what? Imatest somehow knows about the scene? It disregards the RGB rendering?
As to the sunset scene or a candlelit scene, WB will not produce the perceived scene colors, since the eye does not chromatically adapt to such red colors.
So using your yet undefined methods and terminology, this is inaccurate use of WB?
**My public iDisk:
thedigitaldog
Name (lower case) public
Password (lower case) public
Public folder Password is “public” (note the first letter is NOT capitalized).
To go there via a web browser, use this URL:
http://idisk.mac.com/thedigitaldog-Public
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I’ll put it on my public iDisk**.
Thanks. I downloaded the image and looked at in camera raw and noted that it was overexposed and required a large negative exposure correction. ACR wouldn't let me WB on the white patch. I looked at the image in Rawnalize and the green channel is heavily clipped. That is not a good square for white balance. The other neutral patches are intact and give reasonable WB values of about 4150K. As I suspected, your WB was screwed up. Why didn't you use a nonclipped area for the WB?
(http://bjanes.smugmug.com/Photography/White-Balance/i-S8CZvQS/0/O/Snap1.png)
Now what would be proper? Its been handled in LR. Proper would be MelissaRGB using percentage values. And no, the values are probably not proper considering the color appearance doesn’t look anything like the scene (its too warm, as stated).
As I understand Melissa, it uses ProPhotoRGB primaries and linear encoding, but reports the RGB values according to an sRGB tone curve. The percentage values can easily be converted to 8 bit notation. However, I would simply export as a TIFF in ProPhotoRGB. Bruce Lindbloom gives the values for the color checker for ProPhotoRGB and I would compare the values of the patches in your image with what Bruce says they should be. If they match, I would say your capture is accurate. When I get the time I might do that using the faulty WB from patch 1 and a better WB from patch 2.
(http://bjanes.smugmug.com/Photography/White-Balance/i-Htg5tTb/0/O/ProPhoto.png)
Your kidding with that question right?
No, I am not. See above. With this approach all this confusion about scene colorimetry is circumvented. If I have an accurate capture of the color checker and print it out using an accurate profile, I should have a good match to the target. If I use a bad white balance, I suspect the match would be poor.
Its neither pleasing or a good reproduction of the scene BECAUSE of the CURRENT WB. That’s the point! I’m not sure you are reading and understanding what I and others have written (I’m not the first person to suggest this).
Why don't you try using a proper white balance? The others comprise one or two at most. In these forums, I have found that when a lesser known person challenges an authority who behaves in an arrogant and demeaning fashion, not many others wish to join in support of the lesser known author and share in the denigration. Sometimes I receive private messages of support, as I did with the camera color space exchange with you.
Regards,
Bill
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I downloaded the image and looked at in camera raw and noted that it was overexposed and required a large negative exposure correction.
The raw data is absolutely not over exposed. Are you familiar with ETTR? “Negative Exposure” (which is what I rendered in the DNG) is exactly the correct way to normalize the ETTR data. It looks over exposed to your default ACR settings. But like the WB, that’s simply a starting point. It is not necessarily correct or incorrect, accurate or inaccurate. No more than you can look at a color neg and tell us its accurate for a undefined filter pack in an enlarger. The warm condition of the WB, much like the appearance you saw initially is not correct for a proper visual appearance of this image. And that can be changed, the reason we shoot and deal with raw data!
ACR wouldn't let me WB on the white patch.
Well LR did so take that up with Adobe. And you can’t alter Tint/Temp either? Cause I can.
I looked at the image in Rawnalize and the green channel is heavily clipped. That is not a good square for white balance. The other neutral patches are intact and give reasonable WB values of about 4150K. As I suspected, your WB was screwed up. Why didn't you use a nonclipped area for the WB?
Yes, WB is screwed up in that it produces the wrong color appearance. I got a warm appearance because like the initial exposure, that’s not the correct render settings. And it illustrates again, that WB doesn’t ensure “accurate” color. It doesn’t ensure pleasing or desired color (or tone). So much for the simplistic notion that WB fixes all, provides “accurate” color, a point many of us have tried to illustrate to you for a few days now!
As I understand Melissa, it uses ProPhotoRGB primaries and linear encoding, but reports the RGB values according to an sRGB tone curve. The percentage values can easily be converted to 8 bit notation.
Yes, so what? That’s output referred. You continue to ignore this has nothing to do with scene colorimetry. Suppose we open this in another converter that doesn’t use ProPhoto TRC 1.0 for processing and reports a totally different scale for numbers? How does that in any way tell you about the accuracy of the scene data and thus the capture? It doesn’t.
However, I would simply export as a TIFF in ProPhotoRGB.
Until you can answer the question above about the scene colorimetry, it doesn’t matter what space you use. The export provides a set of numbers. Great. Now are they accurate? Well without providing numbers of the scene, you can’t answer that and haven’t from day 1. This continued discussion is really simple, we don’t need to go into color geekdom. You say WB produces accurate color. You have neither described what that means or how you can prove what is accurate. Example. I can take what you say is accurate neutral RGB values (40/40/40) and convert it to an output color space for an Epson and the numbers will be far different and not identical RGB values. So if I provide you just those numbers, you can tell us its neutral or not neutral without knowing about the original color space? No, you can’t. If I send 40/40/40 directly to the Epson, is that a neural color on the print? Nope. But wait, 40/40/40 is an accurate neutral value. Not with the limited data provided, looking solely at this one color space. So tell us how values you see in your raw converter are accurate to the scene. Or how to transform the original scene colors into this color space to prove they are accurate.
If we want to talk about the accuracy of a measurement, say the time at this very second, you can use a sundial, your wrist watch or an Atomic clock. We can argue about the better accuracy of the Atomic clock versus your wrist watch. But we’ll be pretty close without splitting hairs. I’m OK being accurate within a 10th of a second here. But we have values we can use to discuss this time accuracy. We can agree that the sundial may be off X number of minutes and agree to what is a level of accuracy we will accept. We can’t do this with your WB belief system because we don’t even have a value like days, let alone hours or seconds to define accuracy. And we don’t have a method to even gauge the process (the sun dial, your wrist watch). You just want us to believe in some level of accuracy and disbelieve there is any level of subjectively but you refuse to even define the beginnings of a process. If you don’t like me giving you shit about using the term accuracy, then define the accuracy much as we could discuss the accuracy of gauging the time of day to the second! If you can’t do that, then fine, say so. We’ll move on and ignore your mangling of the term accuracy.
With this approach all this confusion about scene colorimetry is circumvented. If I have an accurate capture of the color checker and print it out using an accurate profile, I should have a good match to the target. If I use a bad white balance, I suspect the match would be poor.
Accurate how compared to what? What instrument with which illuminant should I use to measure the Macbeth which then perfectly matches the scene illuminant using any specified transformation? If I have the actual spectral sensitivities of the chip AND the scene illuminant, I might be able to do this. But neither you nor I have that. So we’re back to you saying WB produces accurate color with absolutely no way to back it up.
Can and will you describe how you came up with this accuracy theory?
Why don't you try using a proper white balance?
What do you mean? You told us earlier to WB on white, (you used clouds as an example) and also said quite clearly: For accurate colors, it is usually best to take a WB reading from a neutral card such as a WhiBal. Now you’re bringing in exposure (which isn’t over exposed) and suggesting there is something wrong with the white on the Macbeth. But that’s not really worth going over, its your continuing language that WB produces an accurate rendering which has yet to be explained let alone proven. If you care to enlighten us on how this is produced, we can dig into white cards, exposure and the like. We’re far from that point yet.
The others comprise one or two at most.
I see, they then are wrong as I am. That’s your take. Look, I’m sure I speak for the others. If you can come up with a step by step, scientific process and a metric for accuracy, we’re all ears. So far, you continue to demand that WB isn’t subjective but have provided no mythology to prove that is the case. Or that WB isn’t subjective. My DNG illustrates that what I admit is not the proper white to WB on, disproves your simplistic idea and that I can say this from a totally subjective POV (cause I saw the scene and the rendering and its way off). You’ve got a raw file that can have an almost unlimited degree of alteration to the final numbers and rendering based on the sliders in your raw converter. So prove to us how we move em about to get accurate color, once you define what the accuracy metric is and we you got there. Otherwise, you’re wasting everyone’s time here.
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The raw data is [sic] absolutely not over exposed. Are you familiar with ETTR? “Negative Exposure” (which is what I rendered in the DNG) is exactly the correct way to normalize the ETTR data. It looks over exposed to your default ACR settings. But like the WB, that’s simply a starting point. It is not necessarily correct or incorrect, accurate or inaccurate. No more than you can look at a color neg and tell us its accurate for a undefined filter pack in an enlarger. The warm condition of the WB, much like the appearance you saw initially is not correct for a proper visual appearance of this image. And that can be changed, the reason we shoot and deal with raw data!
The raw data are absolutely overexposed, since the green channel is blown in the raw file as shown by Rawnalize, which looks directly at the raw data without demosaicing. Didn't you look at the raw histogram I posted? This has nothing to do with my ACR settings. I am quite familiar with ETTR to the extent that I know that its rationale is not related to the number of levels in the brightest f/stop of a raw file, but to the signal:noise improvement resulting from increased exposure.
I did look further at the raw file and saw that only the white square of the color checker was blown. You could try to save face by stating that the white square contains no important data and the exposure was thus proper ETTR.
Well LR did so take that up with Adobe. And you can’t alter Tint/Temp either? Cause I can.
Why would I want to take that up with Thomas Knoll? Does he want to enable inexperienced users to white balance on blown channels?
Yes, WB is screwed up in that it produces the wrong color appearance. I got a warm appearance because like the initial exposure, that’s not the correct render settings. And it illustrates again, that WB doesn’t ensure “accurate” color. It doesn’t ensure pleasing or desired color (or tone). So much for the simplistic notion that WB fixes all, provides “accurate” color, a point many of us have tried to illustrate to you for a few days now!
Yes, so what? That’s output referred. You continue to ignore this has nothing to do with scene colorimetry. Suppose we open this in another converter that doesn’t use ProPhoto TRC 1.0 for processing and reports a totally different scale for numbers? How does that in any way tell you about the accuracy of the scene data and thus the capture? It doesn’t.
You can make a table of the color numbers of the color checker in any output space, as Bruce Lindbloom as posted on his web site.
Until you can answer the question above about the scene colorimetry, it doesn’t matter what space you use. The export provides a set of numbers. Great. Now are they accurate? Well without providing numbers of the scene, you can’t answer that and haven’t from day 1.
But I do know the colors of the color checker and I can compare them to the values in the rendered file with a known colors pace. It is indeed simple.
This continued discussion is really simple, we don’t need to go into color geekdom. You say WB produces accurate color. You have neither described what that means or how you can prove what is accurate. Example. I can take what you say is accurate neutral RGB values (40/40/40) and convert it to an output color space for an Epson and the numbers will be far different and not identical RGB values. So if I provide you just those numbers, you can tell us its neutral or not neutral without knowing about the original color space? No, you can’t. If I send 40/40/40 directly to the Epson, is that a neural color on the print? Nope. But wait, 40/40/40 is an accurate neutral value. Not with the limited data provided, looking solely at this one color space. So tell us how values you see in your raw converter are accurate to the scene. Or how to transform the original scene colors into this color space to prove they are accurate.
No I did not say that WB alone will give accurate colors, but proper WB along with a good camera profile will help in producing accurate colors. All current CFA sensors have metameric failure. If RGB values are equal in ProPhotoRGB, the color will be neutral. The Epson is non-linear, and a profile using a lookup table is necessary to take the working space numbers of 40, 40, 40 and convert them to values that will produce the same neutral colors in the print.
What do you mean? You told us earlier to WB on white,...
Well, white patch 1 of the color checker is not neutral, so you didn't white balance on white. Furthermore, no one who knows what he is doing would attempt white balance with a blown channel.
I see, they then are wrong as I am. That’s your take. Look, I’m sure I speak for the others. If you can come up with a step by step, scientific process and a metric for accuracy, we’re all ears. So far, you continue to demand that WB isn’t subjective but have provided no mythology to prove that is the case. Or that WB isn’t subjective. My DNG illustrates that what I admit is not the proper white to WB on, disproves your simplistic idea and that I can say this from a totally subjective POV (cause I saw the scene and the rendering and its way off). You’ve got a raw file that can have an almost unlimited degree of alteration to the final numbers and rendering based on the sliders in your raw converter. So prove to us how we move em about to get accurate color, once you define what the accuracy metric is and we you got there. Otherwise, you’re wasting everyone’s time here.
Look here (http://www.imatest.com/docs/colorcheck.html) at the Colorcheck documentation. You can take a picture of your color checker and determine if the rendered image has color values appropriate for the color space used. If your white balance is off, your colors will be off. What more can I say? This is similar to the camera color space thread where you chose to ignore the opinion of Thomas Knoll and Chris Murphy.
Regards,
Bill
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The raw data are absolutely overexposed, since the green channel is blown in the raw file as shown by Rawnalize, which looks directly at the raw data without demosaicing.
And yet ACR/LR shows zero clipping on the Macbeth.
You could try to save face by stating that the white square contains no important data and the exposure was thus proper ETTR.
Well its not clipped so its moot.
Why would I want to take that up with Thomas Knoll? Does he want to enable inexperienced users to white balance on blown channels?
I suspect you’d get no where with Thomas.
You can make a table of the color numbers of the color checker in any output space, as Bruce Lindbloom as posted on his web site.
Yes you can. Which has no relationship to the scene so how can you say its accurate (for the upteem time)?
No I did not say that WB alone will give accurate colors, but proper WB along with a good camera profile will help in producing accurate colors.
Again, you provide no means to back that up. Either what that means or how to evaluate it from the scene. Its accurate only because you say so.
You continue to ignore the questions asked of you. You continue to talk about clipping that isn’t an issue or plays a role in explaining or providing the accuracy metric or methodology. I’m going to then continue to believe you can’t.
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And yet ACR/LR shows zero clipping on the Macbeth.
Well its not clipped so its moot.
I suspect you’d get no where with Thomas.
You continue to ignore the questions asked of you. You continue to talk about clipping that isn’t an issue or plays a role in explaining or providing the accuracy metric or methodology. I’m going to then continue to believe you can’t.
Give it up! The white square is clipped and you attempted to white balance on a clipped area. ACR/LR is not designed to look at the raw files directly. And I suspect that Thomas would ignore your request to enable white balance on clipped channels, should you be so foolish to make such a requeswt. I have repeatedly told you how I would check the rendered colors of the color checker and compare them to the actual colors of the target. What more can I do? You won't listen. As far as I am concerned, I have proven that you overexposed the target and attempted to white balance on a clipped patch.
I white balanced on patch two and got 4150K, tint +8, which is very close to your auto WB that you felt gave you good results. However, auto WB will not work on scenes having a predominant strong color with no neutrals. It does work when looking at the whole target with many colors and neutral areas.
I rest my case. It is fruitless to attempt a discussion with you as I have seen before, but you again are proven wrong in some areas. You do not know everything.
Regards,
Bill
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Bill the next knock on the door will be from the men in white coats. Please go quietly. You will also find the Digital Dog in the van that will take both of you away for help. BTW I don't think there is room in the van for your stirring stick. ;) ;D
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The white square is clipped and you attempted to white balance on a clipped area.
The numbers say otherwise. At least in this example, actual numbers not the made up ones you’ve yet to define as accurate.
Agreed, done here. I’m taking that spectrally white van off into the sunset (which I would never WB upon)
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Bill the next knock on the door will be from the men in white coats. Please go quietly. You will also find the Digital Dog in the van that will take both of you away for help. BTW I don't think there is room in the van for your stirring stick. ;) ;D
Before they carry me off to the funny farm, I would like to make one final post demonstrating how I proposed to analyze the images. The first step is to check for channel clipping. Rawnalize (http://www.oitregor.com/numeric/Rawnalyze/Rawnalyse_doc/datas/Image.htm#modes) can look directly at the raw file, thus avoiding complications concerning raw converter settings. One can show clipped channels directly as shown below for white patch 1 of the Digital Dog's image. The colors show areas that are not clipped--thus the green areas represent no clipped green, and the magenta areas represent no clipped red or blue.
(http://bjanes.smugmug.com/Photography/White-Balance/i-ND8g9gr/0/O/RawnalizeClipping.png)
One can also get the raw channel values expressed in data numbers or data numbers expressed in 8 bit notation for more convenient analysis. Since this image was taken at high ISO, the standard deviations are rather large but one can look at the mean value as well as the maxima and minima.
(http://bjanes.smugmug.com/Photography/White-Balance/i-DWdSQBH/0/O/RawnalizePatch1.png)
An independent way to analyze the raw file is to use DCRaw. In this case, I used -v -4 -T -o 0 -r 1 1 1 1 to output 16 bit linear raw data. One can examine the resulting TIFF in photoshop using the histogram and color sampler tool to get results similar to those from Rawnalyze, thus verifying the methodology. The green channel is clearly clipped in patch 1.
(http://bjanes.smugmug.com/Photography/White-Balance/i-MtrztVB/0/O/DigDogPSHistogram.png)
One can then analyze the color checker images with various raw converter settings to check for color accuracy using Imatest. Problems with scene referred color do not arise, since we know the true colors of the color checker from published data. It is best to adjust exposure so that Imatest gives a minimal exposure error. Otherwise luminance differences between the observed and thoretical will add to the DeltaE. The original image gave a +0.3 EV exposure error, so I decreased the Digital Dog's exposure setting from -1.20 to -1.53 and left the other settings the same for the initial analysis using the original WB of 5100K.
I then set the WB properly by clicking on the 2nd white patch in ACR and repeated the analysis. The results are shown in graphical form for brevity and clarity. The deltaE's and DeltaC's are better for the proper white balance and hence the results are more accurate with a proper white balance. The original WB was improperly taken and gave poor results. To learn more about Imatest and the interpretation of the results, please see the Imatest documentation (http://www.imatest.com/docs/colorcheck.html#output).
(http://bjanes.smugmug.com/Photography/White-Balance/i-XCdsRSv/0/O/XriteCompositeExpCorr.png)
(http://bjanes.smugmug.com/Photography/White-Balance/i-m5wPmjM/0/O/XriteCompositeColorErrExpCorr.png)
Comments are welcome.
Regards,
Bill
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Interesting discussion. I just would like to mention that the white patch in the colorchecker (image by Andrew Rodney) is indeed clipped at the Raw level, as indicated by Rawnalize and observed by bjanes. I too downloaded the image for checking, I hope you don't mind.
There is no doubt about this.
What happens with LR/ACR is that when you apply negative exposure, highlight recovery will be automatically invoked in case there is any Raw clipping. This is why after applying -1.2 fstops of negative exposure you don't see any clipped values in ACR/LR.
Eric Chan himself explained this behavior of LR/ACR in this thread (http://www.luminous-landscape.com/forum/index.php?topic=36161.msg296883#msg296883)
Now, some versions of ACR won't let you WB on that patch as bjanes mentioned.
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The numbers say otherwise. At least in this example, actual numbers not the made up ones you’ve yet to define as accurate.
Agreed, done here. I’m taking that spectrally white van off into the sunset (which I would never WB upon)
You may be out of here because you have run out of arguments, after having made one last ditch effort to show that your patch was not clipped. You are basically using highlight recovery, which can be used as long as all channels are not clipped (which they were not in your case).
Others can see my detailed analysis, conclusively proving that the green channel was clipped in patch 1. That explains your defective white balance. No way to get out of this one by bluffing and repeating erroneous assertions ad naseum.
Regards,
Bill
Regards,
Bill
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Others can see my detailed analysis, conclusively proving that the green channel was clipped in patch 1.
And that in what way answers the questions asked of you about the methodology and matrix used to define accuracy? None. The clipping BTW IS seen in a specular highlight above the target itself from the metal bar holding the target. Again, so what?
I proposed with this example (which you continue to use to ignore the real debate here, your undefined methodology for the term accurate) to illustrate how WB can fail. Nothing more. You made a very simplistic statement about WB which like Herman Cain, you are now backing away from. I think I proved your simplest statement doesn’t wash. You want to ignore that and go down a rabbit hole about clipping, how ACR versus LR do or do not let you click there etc. Point is, WB can be totally wrong. I told you that clicking on the 2nd patch is a better move long ago. Would you like me to expose less to the right such there is no clipping anywhere? Would that then get you on the topic, explaining the so called accuracy metric and methodology? I doubt it.
I wish I hadn’t provided the “here’s an example of how WB fails and doesn’t produce accurate color” part of all this, it was a great way for you to circumvent the basis of my original post about your poor use of language (WB produces accuracy). You’ve been asked a number of times how one correlates this ‘fact’ based on the scene colorimetry. You haven’t nor do I believe you can. You ignored the time accuracy analogy. In that example, we have methods and values we can use to define what is accurate and by what degree. Instead you focus on clipping. Its obvious to me you just want to throw out terms of your making and can’t provide any evidence that any WB is colorimetrically accurate or that WB isn’t subjective.
Here’s what you need to do if you can. Explain what you mean by accurate using a process we can follow to prove that a specific WB process produces accuracy to the scene, then some metric value to define what is and isn’t accurate.
If I measure two patches with a Spectrophotometer, I can tell you how close, (how accurate) the two values are using a specific dE formula. I can then suggest that a dE value of X produces an acceptable match and a value that doesn’t. We can easily agree that a dE 2000 value of less than one is a visual match. We can agree that a dE of 4+ isn’t. We can define a process (measure the two colors in X software, set it to use this dE formula). Anyone with the equipment and software can produce this set of tests. When we say “this patch matches that patch” we are not pulling a statement out our ass. If we wish to define the accuracy of a profile we built, we can do a similar test with thousands of patches. We can calculate an average, max, min, Stan DV and make a non ambiguous statement about the accuracy of the profile. Or I can just say “this profile is accurate”, not provide any methodology and expect you to take my word for it. Without such a test process the statement is pure BS. I think your “WB=accuracy” is BS. Prove me wrong using some defined process like the example above (or the time accuracy example). You are entitled to your own opinions but not your own facts. Make your statement fact based! Can you? Still waiting. Or you can move on or be dismissive and talk about exposure and clipping.
If I come here and say, I looked at two similar patches and they appear inaccurate, that’s subjective and you or anyone else with the two patches, under the same conditions can agree or disagree. Only when we agree upon a method of measuring the two, specifying the conditions and the metric can we be non ambiguous. Your original statement has and continues to be total ambiguous and non fact based.
You stated many posts ago that WB produces an accurate rendering. Prove it. To do so you need to define how you came to this conclusion. You haven’t and I suspect can’t. There is a target we could agree upon, the Macbeth. Its under some undefined illuminant and in your “WB produces accurate color” that can greatly change. WB under all illuminants produces this accuracy? Yes or no? You measured what at the scene to define this accuracy? You transformed the data from scene to output referred how to correlate this accuracy? You’re using dE or something else to describe the accuracy? Are you taking your accuracy based on solid colors or many colors in context? How many? ALL the colors in the target are accurate? If not all, what’s the average, max and min accuracy values?
Instead you simply say “this is accurate” which seems to be pulling a bogus statement out of your butt. We’ve been over this a dozen times. You say its accurate, I say prove it and tell me by how much within the image. You are further convinced that this isn’t subjective so again, you’ll prove this is a measurable and not a appearance modeling issue how?
Its funny how you say I don’t answer questions (the pot calling the kettle black). You started this WB accuracy idea, can you prove it?
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And that in what way answers the questions asked of you about the methodology and matrix used to define accuracy? None. The clipping BTW IS seen in a specular highlight above the target itself from the metal bar holding the target. Again, so what?
There is clipping not only in the area you indicated, but also in the white patch, where you deny clipping took place. What about my analysis. Can you respond to that?
I proposed with this example (which you continue to use to ignore the real debate here, your undefined methodology for the term accurate) to illustrate how WB can fail. Nothing more. You made a very simplistic statement about WB which like Herman Cain, you are now backing away from. I think I proved your simplest statement doesn’t wash. You want to ignore that and go down a rabbit hole about clipping, how ACR versus LR do or do not let you click there etc. Point is, WB can be totally wrong. I told you that clicking on the 2nd patch is a better move long ago. Would you like me to expose less to the right such there is no clipping anywhere? Would that then get you on the topic, explaining the so called accuracy metric and methodology? I doubt it.
There is no need to introduce racist comments about Mr. Cain in the discussion. You might know that you should take the white balance from a nonclipped area, but you didn't know that patch 1 was clipped and you still won't admit it. The white balance issue is important because your post suggested that white balancing on a neutral area can be misleading and automatic WB can work better. It certainly will work better if the WB in the first instance is faulty. Your demonstration is worthless. Can't you read the graphs I posted? They express DeltaEs and DeltaCs. I could post Excel worksheets giving the data in tabular format. What more do you want?
Regards,
Bill
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There is clipping not only in the area you indicated, but also in the white patch, where you deny clipping took place. What about my analysis. Can you respond to that?
According to LR and ACR, there is no clipping after normalization. But even if I admit there is, without knowing why those products clearly show values less than 100%/255, will you now finally and fully answer the questions asked of you multiple times?
There is no need to introduce racist comments about Mr. Cain in the discussion.
Racist? Where would that be? I’m simply pointing out you, like Mr, Cain seem to change stories.
Can't you read the graphs I posted? They express DeltaEs and DeltaCs.
And they correlate how to the actual scene values? Where would those values be? Or you feel, the raw values alone (you presumably report), tell us everthing about the scene conditions, including the illuminant and the scene colorimetry? The scene colorimetry has no bearing on the resulting values you claim are accurate?
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Bill the next knock on the door will be from the men in white coats. Please go quietly. You will also find the Digital Dog in the van that will take both of you away for help. BTW I don't think there is room in the van for your stirring stick. ;) ;D
There is no need to introduce racist comments about Mr. Cain in the discussion.
Bill
The stirring stick used in the second quote is Redwood sized....ridiculous.
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Lookee what happens when you leave the computer to go and have a nice dinner.
Bill, it's Friday night. Go have a beer or whatever your preferred libation at your local and loosen up a bit.
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Moderator, please put them out of their misery and lock this thread. :)
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Moderator, please put them out of their misery and lock this thread. :)
Oh! Oh! Wait! Not before I have my say about ETTR.
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According to LR and ACR, there is no clipping after normalization. But even if I admit there is, without knowing why those products clearly show values less than 100%/255,
Why don't you admit the obvious?
will you now finally and fully answer the questions asked of you multiple times and they correlate how to the actual scene values? Where would those values be? Or you feel, the raw values alone (you presumably report), tell us everthing about the scene conditions, including the illuminant and the scene colorimetry? The scene colorimetry has no bearing on the resulting values you claim are accurate?
You keep referring to “scene referred” and “output referred”, probably merely for obfuscation and intimidation of anyone who disagrees with you. For an authoritative reference on scene referred and output referred data, I have used Rendering the Print: the Art of Photography (http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf) by Dr. Karl Lang. He covers scene referred data output referred data and rendering from input referred to output referred data.
For most purposes one does not want scene referred data, which is a good thing, since it is not possible to get true scene referred data from a digital camera. As Dr. Lang explains if one wants to capture the actual wavelengths and energy values in the scene, one way would be “to record our scene would be a perfect scientific capture called a spectral pixmap. The image plane would be divided up into a grid of pixels (picture elements); for each pixel we would record 300 values representing the energy for each wavelength of visible light. Spectral pixmaps are huge. A 10-million pixel image would be 5.8 gigabytes.”
This would require a spectrophotometer to record the spectral pixmap and one could derive tri-stimulus values producing a metameric match to the recorded values in the pixmap using the CIE standard observer data. A colorimeter uses filters to record a tri-stimulus value, and the CFA in the digital camera does the same. According to Dr. Lang, “The raw data read from the sensor chip is called scene-referred data. The numeric values have a direct relationship to the energy of light that was present in the original scene. The only thing missing are the portions of the scene above or below our ‘exposure window’.” Further, he states, “All forms of photography other than creating a spectral pixmap are imperfect, and can only represent an approximation of the original scene. Whether film or digital, the data we start with is already significantly limited by the method of capture. In human terms those limited factors are dynamic range, color gamut, and color accuracy.” It is the last term that makes the hair on the back of your neck stand up.
Of course, neither I nor you can produce accurate scene referred data with a digital camera, but the raw file is the best approximation since, according to Dr. Lang “The Raw file is the complete scene-referred image, as seen by the camera’s sensor…”. Furthermore, I am not interested in scene referred color in terms of the actual wavelengths in the scene, but rather want data chromatically adapted to a standard space such as ProPhotoRGB (white point of D50). The observer will adapt to the color temperature of the scene, but the camera will not, and a white point for the scene is needed to chromatically adapt the data.
The ICC (http://www.color.org/scene-referred.xalter) gives a method to obtain scene referred data in Photoshop and ACR. Even though ProphotoRGB is intended for storing of output referred data, it differs from the scene referred RIMM space only by gamma encoding of the data. Of course, ACR needs an accurate camera profile to convert the color recorded in the raw file to its internal working space which is RIMM. Considerably different values are obtained the Adobe Standard profile and various other camera profiles. An accurate white balance is also needed for this process. One can then store the file in ROMM for further processing. At this point, the scene luminances are clipped to the dynamic range of the camera and no accounting for flare light has been performed. This is not final output data, since mapping of the luminances to the DR of the output device and the colors of the scene to the gamut of the output device has not been performed, but rather has been left for later processing. One does not want data for a specific output device at this point. Generally, that is left to the profile for the printer or other output device. Furthermore, the output rendering strives to produce a pleasing rather than accurate reproduction in most cases. That is the art of rendering as Dr. Lang discusses.
Now I can explain my method to obtain scene referred color and check the accuracy of the capture. If I take a shot of a color checker with my digital camera, the raw file contains scene referred data within the limitations described above. I can render the image into ROMM (ProPhotoRGB) with ACR, which needs white balance to accomplish the process. To obtain scene referred luminances, I could convert to RIMM. Since the color values and luminances of the checker are known, I can then compare the observed value of a given patch from the actual values of the color checker, using Imatest for convenience. It is not necessary to convert to RIMM, since Imatest can use ROMM. Accuracy can be expressed as ΔE or ΔC. This is what I have done with my previous posts which you find so disconcerting. Now I await your response.
Regards,
Bill
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You keep referring to “scene referred” and “output referred”
Simple, its the only way to prove colorimetric accuracy as I've tried to explain to you half a dozen times. If you can measure the illuminant and the actual colors of the scene using that process, the camera itself (spectral sensitivities) you can define the source values. Then you can define the results of the data you end up (which is a big set of possibilities depending on processing) with and provide an accuracy metric. Otherwise you're comparing apples and oranges.
probably merely for obfuscation and intimidation of anyone who disagrees with you.
Not at all. I'm asking for accuracy to be defined properly based on the scene, the capture and the resulting values so accuracy is not a subjective term. It has actual meaning.
For most purposes one does not want scene referred data, which is a good thing
This was all covered in the ICC white paper! It agrees with Karl (who's a partner of mine!).
Of course, neither I nor you can produce accurate scene referred data with a digital camera
And yet you continue to claim that data is accurate with WB and never subjective, and you continue to ignore requests for how such a value is calculated. Can't we stop this silly debate until you do so? Again, WB makes the data accurate based on scene colorimetry?
Further, he states, “All forms of photography other than creating a spectral pixmap are imperfect, and can only represent an approximation of the original scene.
And yet your use of WB produces accurate color?
ACR needs an accurate camera profile to convert the color recorded in the raw file to its internal working space which is RIMM.Considerably different values are obtained the Adobe Standard profile and various other camera profiles. An accurate white balance is also needed for this process.
Here we go again! So like the "WB makes the image accurate" what technique makes your profile accurate based on the scene colorimetry?
Furthermore, the output rendering strives to produce a pleasing rather than accurate reproduction in most cases
But that is accurate and not subjective? We all know the answer to that.
I place a Macbeth under some illuminant (lets say its at sunset). You can define those colors, then scene colorimetry, then end up with an output referred image as we've been playing with in this post and tell us with or without WB or any other set of slider use or DNG profile its accurate?
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BTW, this just up on the ColorSync list in terms of Imatest. Google Iliah if you must.
"Since there is no such thing as a gamut for an input device, then
there is no way to compute it or calculate a figure of merit."
Maybe Imatest?
Imatest colour evaluation is not dealing with raw files, so you have both camera and raw converter peculiarities at Imatest's input. There is no way in Imatest to separate one from another.
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Iliah Borg
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You keep referring to “scene referred” and “output referred”, probably merely for obfuscation and intimidation of anyone who disagrees with you. For an authoritative reference on scene referred and output referred data, I have used Rendering the Print: the Art of Photography (http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf) by Dr. Karl Lang.
Karl's a bright boy but but he ain't a Dr. (not sure he even finished any advanced degree)
Any time you guys wanna quit pissing on the tree, feel free. I don't have the desire to keep parsing each and every item. But I thought it would be useful to make sure Karl was referred to correctly, it's Mr. Lang.
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Simple, its the only way to prove colorimetric accuracy as I've tried to explain to you half a dozen times. If you can measure the illuminant and the actual colors of the scene using that process, the camera itself (spectral sensitivities) you can define the source values. Then you can define the results of the data you end up (which is a big set of possibilities depending on processing) with and provide an accuracy metric.
If you want true scene referred data, you merely reproduce the luminances and color values of the scene, and the information concerning the illuminant is not needed. For an explanation, consider the following.
At any location in a scene, the ambient light is specified by its spectral power distribution, E(λ), which describes the energy per second at each wavelength λ. The ambient light is reflected from the surfaces of the scene and focused on the photodetector element of the eye or digital sensor. The proportion of light of wavelength λ toward location x on the sensor is determined by the surface spectral reflectance, Sx(λ). The signal will be described by the function E(λ)Sx(λ). We can determine the overall response of the entire scene by integration.
Now if you want scene referred data, say for a sunset, that would be described by E(λ)Sx(λ) integrated over the entire scene, and this could be measured accurately with three dimensional spectroscopy by creating a spectral pix map. For scene referred data, you need no information regarding the illuminant, since you only want a spectral map of the scene and are measuring the reflected light directly. You could then calculate tri-stimulus RGB values to represent your image. You would still have to deal with chromatic adaption by the observer if you wanted to simulate how the image is perceived by the observer. At sunset, the observer would be adapted to the ambient sunset light. For a less accurate measurement you could use the raw camera image, substituting the camera, which produces scene referred data, for the spectrophotometer.
However, for most photography we want to learn something about the spectral reflectance properties (the color) of the object being photographed, and you would solve the above function for Sx. If the illuminant follows the spectrum of a black body radiator, you could the color temperature of the illuminant instead of E(λ), and the white balance data would be essential for this calculation. Using these data, you could reconstruct the appearance of the object under any illuminant.
For details of the above process, please refer to Maloney (http://www.lecs.cs.ucla.edu/~cyclops/summer07/relatedWork/maloney.pdf) and Maloney and Wandell (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.6.4745&rep=rep1&type=pdf).
And yet you continue to claim that data is accurate with WB and never subjective, and you continue to ignore requests for how such a value is calculated. Can't we stop this silly debate until you do so? Again, WB makes the data accurate based on scene colorimetry?
And yet your use of WB produces accurate color?
Here we go again! So like the "WB makes the image accurate" what technique makes your profile accurate based on the scene colorimetry?
White balance is used as a substitute for the spectral power distribution of the illuminant. Using the WB, one can calculate color values for the image, and an accurate WB is needed for this purpose.
I place a Macbeth under some illuminant (lets say its at sunset). You can define those colors, then scene colorimetry, then end up with an output referred image as we've been playing with in this post and tell us with or without WB or any other set of slider use or DNG profile its accurate?
A sunset is a special consideration, but could be handled as described above. However, for sunsets the visual system is not chromatically adapted, so you will have problems with white balance. Bruce Fraser once suggested to me in a post that one can white balance on the whitecaps of waves (presuming one is on the ocean), but I haven't tried that. Experience has told me that daylight WB can be used and the image adjusted to taste. Colorimetric accuracy is not needed in this case.
In general, I don't want my image to be output defined in terms of a printer or monitor. I want the scene colors expressed in ProPhotoRGB so that I can repurpose them for any display. ProPhotoRGB is an output referred space, but I do not want to render the image to accommodate the dynamic range and color gamut of the output device at this time. You are getting hung up on scene referred and output referred without actually taking into account what is needed for practical work.
Regards,
Bill
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BTW, this just up on the ColorSync list in terms of Imatest. Google Iliah if you must.
Imatest colour evaluation is not dealing with raw files, so you have both camera and raw converter peculiarities at Imatest's input. There is no way in Imatest to separate one from another.
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Iliah Borg
Of course a camera does not have a gamut, as explained in part 255 of the Munsell Imaging FAQ. They do explain how the figure of merit for an input device is calculated:
"Since there is no such thing as a gamut for an input device, then there is no way to compute it or calculate a figure of merit. Generally, the accuracy of color capture devices is assessed through the accuracy of the output values for known inputs in terms of color differences. Also, sensors are sometimes evaluate in terms of their ability to mimic human visual responses (and therefore be accurate) using quantities with names like colorimetric quality factor, that measure how close the camera responsivities are to linear transformations of the human color matching functions. Doing an internet search on "colorimetric quality factor" will lead you in the right direction."
This is what I have been trying to do using the known values of the color checker as output by the camera using ACR to render the files. One needs to measure the color of the illuminant, done approximately with the WB eyedropper. With such systems, accuracy is only relative, and we are trying to maximize it.
Now rather than obfuscating and nit picking about how I can't achieve the impossible, why don't you present some data and contribute to the discussion in a useful way?
Regards,
Bill