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Author Topic: Camera White Balance and Post Processing  (Read 37650 times)

bretedge

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Re: Camera White Balance and Post Processing
« Reply #40 on: October 31, 2011, 03:24:02 am »

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.

bjanes

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Re: Camera White Balance and Post Processing
« Reply #41 on: October 31, 2011, 10:41:43 am »

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, 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.



Setting the color balance to daylight helps. ACR gives a WB of 5500K.



A more accurate WB can be taken from another image containing a white cloud as a reference point.



One can apply this WB setting to the flower image to obtain a more accurate rendering of the actual appearance of the flower.



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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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #42 on: October 31, 2011, 10:50:02 am »

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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bjanes

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Re: Camera White Balance and Post Processing
« Reply #43 on: October 31, 2011, 11:19:39 am »

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 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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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #44 on: October 31, 2011, 11:24:05 am »

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 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.

Quote
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.
« Last Edit: October 31, 2011, 11:26:20 am by digitaldog »
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RFPhotography

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Re: Camera White Balance and Post Processing
« Reply #45 on: October 31, 2011, 11:44:20 am »

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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bjanes

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Re: Camera White Balance and Post Processing
« Reply #46 on: October 31, 2011, 01:10:21 pm »

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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bjanes

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Re: Camera White Balance and Post Processing
« Reply #47 on: October 31, 2011, 01:32:16 pm »

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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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #48 on: October 31, 2011, 01:41:10 pm »

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"

Quote
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?
« Last Edit: October 31, 2011, 01:44:56 pm by digitaldog »
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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #49 on: October 31, 2011, 01:43:48 pm »

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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bjanes

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Re: Camera White Balance and Post Processing
« Reply #50 on: October 31, 2011, 01:51:56 pm »

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.

Regards,

Bill
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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #51 on: October 31, 2011, 01:54:26 pm »

A better discussion of image rendering is given by Karl Lang.

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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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #52 on: October 31, 2011, 01:59:21 pm »

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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bjanes

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Re: Camera White Balance and Post Processing
« Reply #53 on: October 31, 2011, 02:09:50 pm »

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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hjulenissen

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Re: Camera White Balance and Post Processing
« Reply #54 on: October 31, 2011, 02:10:31 pm »

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
« Last Edit: October 31, 2011, 02:18:32 pm by hjulenissen »
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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #55 on: October 31, 2011, 02:28:34 pm »

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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jeremypayne

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Re: Camera White Balance and Post Processing
« Reply #56 on: October 31, 2011, 03:47:14 pm »

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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Tim Lookingbill

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Re: Camera White Balance and Post Processing
« Reply #57 on: October 31, 2011, 04:33:38 pm »

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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bjanes

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Re: Camera White Balance and Post Processing
« Reply #58 on: October 31, 2011, 06:08:19 pm »

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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digitaldog

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Re: Camera White Balance and Post Processing
« Reply #59 on: October 31, 2011, 07:09:58 pm »

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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