Luminous Landscape Forum

Raw & Post Processing, Printing => Colour Management => Topic started by: Robert Boire on September 26, 2010, 12:25:48 pm

Title: Adobe RGB vs sRGB
Post by: Robert Boire on September 26, 2010, 12:25:48 pm
Hello,

I know that Adobe has a wider gamut than sRGB. However are their situations when sRGB is in fact preferred?

I ask because my Canon user manual states "Adobe RGB is not recommended if you do not know about image processing, Adobe RGB and Design Rule for Camera File System 2.0", which in fact pretty much tells me nothing at all.

Thanks

R
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on September 26, 2010, 01:25:36 pm
...which in fact pretty much tells me nothing at all...

Short answer: if so, stick to sRGB.

Long answer: Depends on whether you shoot RAW or jpeg. Also depends on your desired output, i.e., whether you post-process your images (in Photoshop or similar), and whether you print them at home or online lab, or you simply upload them to web sites.

If you shoot RAW, the camera setting (i.e. Adobe RGB vs. sRGB) does not matter (but might influence how accurately camera LCD displays pictures)

If you shoot jpeg, intend to post-process it and print at home, go Adobe RGB

If you shoot jpeg, intend to post-process it, but want to print it online (or send to web sites), set your camera to Adobe RGB, process it as such, and convert to sRGB as the last step in post-processing

If you shoot jpeg, but do not want to post-process it, just to use it on the web or for online lab printing, stick to sRGB

These are simplified, rule-of-thumb suggestions, that take into account your current apparent knowledge of the subject (as perceived by me, of course). I hope you'll find them helpful.




Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on September 26, 2010, 03:10:16 pm
I know that Adobe has a wider gamut than sRGB. However are their situations when sRGB is in fact preferred?

Publishing on the web or handing off images to people who don't understand color management.
Title: Re: Adobe RGB vs sRGB
Post by: Robert Boire on September 26, 2010, 07:59:05 pm
Actually this is helpful... except for the short answer of course.


If you shoot RAW, the camera setting (i.e. RAW vs. sRGB) does not matter (but might influence how accurately camera LCD displays pictures)


I think you mean "Adobe vs sRGB"? In fact I have been shooting RAW recently. Can you explain "influence how accurately camera LCD display pictures". How does the choice of color space affect the LCD. For that matter what color space does the LCD use?
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on September 26, 2010, 09:17:54 pm
The LCD shows you what you'd get if you shot JPEG. But you shoot raw so the histogram and rendering you see has no real bases on the actual raw data nor how it will be rendered in at this point, an undefined raw converter using an undefined set of rendering settings. IOW, the stuff on the back of your camera is quite accurate if you shoot JPEG and a huge stretch if you shoot raw.
Title: Re: Adobe RGB vs sRGB
Post by: Robert Boire on September 26, 2010, 09:50:17 pm
The LCD shows you what you'd get if you shot JPEG.

So if am shooting raw for is post-processing possibilities, I should also shoot jpeg so that my LCD is reasonably useful?

Also is itpreferable to use the camera manufacturer's raw converter as opposed to - for example- what is available with Photoshop?

Thanks
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on September 26, 2010, 09:52:45 pm
Actually this is helpful... except for the short answer of course.

The short answer was meant to be helpful for the situation where you really do not want to know, nor you care, about color management issues.

Quote
...I think you mean "Adobe vs sRGB..."?

Yes, sorry, typo... already corrected it in the post above.

Quote
... Can you explain "influence how accurately camera LCD display pictures". How does the choice of color space affect the LCD. For that matter what color space does the LCD use?

Even when you shoot RAW exclusively, the camera can not display RAW on its LCD, but has to create an on-the-fly jpeg for that purpose. If you do not set your custom jpeg settings, the camera would use its defaults. If you do set it, you can usually adjust contrast, saturation and sharpness, in addition to color space.

What I try to do is to set all those parameters so that the image on the LCD better matches the reality in front of the lens. Try doing it with something containing bright red, as there you would see the most apparent difference between an image on the LCD shot with Adobe RGB and the one with sRGB.
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on September 26, 2010, 10:14:10 pm
... the stuff on the back of your camera is quite accurate if you shoot JPEG and a huge stretch if you shoot raw.

Pardon my ignorance, but isn't "a huge stretch" a huge stretch?
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on September 26, 2010, 10:37:35 pm
So if am shooting raw for is post-processing possibilities, I should also shoot jpeg so that my LCD is reasonably useful?

Also is itpreferable to use the camera manufacturer's raw converter as opposed to - for example- what is available with Photoshop?...

Again, the short answer would be "no" in both cases.

Even if you do not shoot jpeg, the camera will create one on-the-fly for display purposes. As for manufacturer's own RAW converter, there are very few instances where it might be more convenient (though not necessary) to use it. One of those instances might be when manufactures create new custom profiles, e.g., "landscape", "portrait", "faithful"  etc., which then add tags to RAW files, so that when you open them in their own converter, the display would create on-the-fly jpeg, taking those tags into account. It takes then certain time for other RAW converters (e.g., Adobe's) to catch up and incorporate them. In the meantime, one might argue that using own converter might be more convenient, if you insist on using those profiles.
Title: Re: Adobe RGB vs sRGB
Post by: bjanes on September 27, 2010, 07:29:36 am
The LCD shows you what you'd get if you shot JPEG. But you shoot raw so the histogram and rendering you see has no real bases on the actual raw data nor how it will be rendered in at this point, an undefined raw converter using an undefined set of rendering settings. IOW, the stuff on the back of your camera is quite accurate if you shoot JPEG and a huge stretch if you shoot raw.

I think that this answer requires clarification. Whether the camera records raw data or JPEG encoded data, it creates a JPEG encoded preview image using the settings on the camera, which include the color space (sRGB or aRGB), contrast, sharpening and other parameters. This JPEG preview is also used to construct the camera luminance and color histograms. Color management for the camera LCD is not usually documented, but presumably the camera uses some type of profile to translate the RGB values of the JPEG file to values that would display accurately on-screen. To the extent that this color management is successful, the color space set on the camera would not affect the appearance of the preview image. This is analogous to Photoshop, where the image that appears on the screen is same whether one is using sRGB or ProphotoRGB, provided that colors are not clipped.

If you render the raw file using the camera manufacturers raw converter, the converter will read the camera settings and produce the same appearance that would be obtained from an in camera JPEG with those settings. On the other hand, Camera Raw does not read the settings and uses its default profile. However, Adobe does supply camera profiles that will produce results very similar to those obtained with some of the camera settings.

Bill
Title: Re: Adobe RGB vs sRGB
Post by: stamper on September 27, 2010, 08:05:34 am
I think that this answer requires clarification. Whether the camera records raw data or JPEG encoded data, it creates a JPEG encoded preview image using the settings on the camera, which include the color space (sRGB or aRGB), contrast, sharpening and other parameters. This JPEG preview is also used to construct the camera luminance and color histograms. Color management for the camera LCD is not usually documented, but presumably the camera uses some type of profile to translate the RGB values of the JPEG file to values that would display accurately on-screen. To the extent that this color management is successful, the color space set on the camera would not affect the appearance of the preview image. This is analogous to Photoshop, where the image that appears on the screen is same whether one is using sRGB or ProphotoRGB, provided that colors are not clipped.

If you render the raw file using the camera manufacturers raw converter, the converter will read the camera settings and produce the same appearance that would be obtained from an in camera JPEG with those settings. On the other hand, Camera Raw does not read the settings and uses its default profile. However, Adobe does supply camera profiles that will produce results very similar to those obtained with some of the camera settings.

Bill

If you up saturation, contrast etc would that not affect the histogram and make you think that the image has possibly overblown highlights when in fact there isn't any?
Title: Re: Adobe RGB vs sRGB
Post by: bjanes on September 27, 2010, 08:43:42 am
If you up saturation, contrast etc would that not affect the histogram and make you think that the image has possibly overblown highlights when in fact there isn't any?

Quite true. The histograms represent the rendered preview file, not the raw file. The color response of most modern digital cameras is quite high and one really should render into ProPhotoRGB or a similar wide space to avoid saturation clipping. Unfortunately such a wide space is not offered with most cameras. Even with normal settings, the color histograms can show saturation clipping when none is present in the raw file, and the situation can be made worse by a high contrast tone curve. Ideally, a contrast curve would not affect the extreme highlights, but many cameras allow for highlight headroom and a high contrast tone curve can cause clipped histograms. Fore these reasons, many photographers set the camera to normal or low contrast and saturation. White balance can also cause clipping in the red and blue channels when the raw file is intact. Some photographers use UniWB to prevent this.

Bill
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on September 27, 2010, 01:01:31 pm
... Color management for the camera LCD is not usually documented, but presumably the camera uses some type of profile to translate the RGB values of the JPEG file to values that would display accurately on-screen. To the extent that this color management is successful, the color space set on the camera would not affect the appearance of the preview image...

On my Canon 40D, there is a slight, but noticeable difference on the LCD screen, depending on the color space chosen.
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on September 28, 2010, 03:32:59 pm
Pardon my ignorance, but isn't "a huge stretch" a huge stretch?

A stop or more difference between what the LCD indicates is clipping (on the JPEG) when there isn’t a lick of clipped data in the raw seems like a pretty huge stretch to me.
Title: Re: Adobe RGB vs sRGB
Post by: Robert Boire on September 29, 2010, 09:23:45 pm
Well for what its worth when I set up my camera to record both the jpeg and RAW  as seen on my computer monitor the difference after looking at a random sample is barely discernible and they look pretty much like what I see on the LCD. Now if only all three could match the scene itself...

BTW I read somewhere that shooting in Adobe will cause pictures to appear "subdued" on a monitor. Is this true any why?
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on September 30, 2010, 09:53:05 am
Well for what its worth when I set up my camera to record both the jpeg and RAW  as seen on my computer monitor the difference after looking at a random sample is barely discernible and they look pretty much like what I see on the LCD.

Now read the article here on Expose to the Right, then actually test that. What you’ll see is that ETTR with proper “normalization” settings in the converter now produces a preview that matches the JPEG yet you “over exposed” (some would suggest properly expose) the raw data. And the matching JPEG with the same raw exposure? Its way blown out. There’s a really big disconnect between the raw data and the JPEG when you capture the raw data for raw (not JPEG) exposure.
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on September 30, 2010, 10:20:09 am
Well for what its worth when I set up my camera to record both the jpeg and RAW  as seen on my computer monitor the difference after looking at a random sample is barely discernible ...

What difference are we talking about here? Between jpeg and RAW, or between sRGB and Adobe RGB, or...?
Title: Re: Adobe RGB vs sRGB
Post by: bjanes on September 30, 2010, 10:31:58 am
A stop or more difference between what the LCD indicates is clipping (on the JPEG) when there isn’t a lick of clipped data in the raw seems like a pretty huge stretch to me.
The correlation between the camera histogram and the raw histogram depends on the camera. It may be one stop for cameras that allow a lot of highlight headroom, but less with others that allow less headroom. The user should check to see what happens with his/her camera.

For the Nikon D3, I photographed a Stouffer wedge using bracketed exposures and the Standard picture control. The shot on the left (1/25 s, f/8) shows highlights just to the left of clipping on the camera histogram and 1/3 stop below clipping in the green channel on the raw histogram as shown by Rawnalize.  Increasing the exposure by 0.3 EV (1/20 s, f/8) causes clipping on the camera histogram and the raw histogram is slightly clipped in the green channel (vertical dotted line indicates clipping). The camera histogram is pretty reliable on this camera.

Title: Re: Adobe RGB vs sRGB
Post by: stamper on September 30, 2010, 11:13:06 am
This subject has been discussed in detail before under the heading Uni White Balance. A very long thread that didn't really come to anything conclusive? ::)
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on September 30, 2010, 11:23:54 am
The correlation between the camera histogram and the raw histogram depends on the camera. It may be one stop for cameras that allow a lot of highlight headroom, but less with others that allow less headroom. The user should check to see what happens with his/her camera.

Absolutely. You have to test your camera, your meter(s) and the effect of the raw converter on clipping.

Quote
For the Nikon D3, I photographed a Stouffer wedge using bracketed exposures and the Standard picture control. The shot on the left (1/25 s, f/8) shows highlights just to the left of clipping on the camera histogram and 1/3 stop below clipping in the green channel on the raw histogram as shown by Rawnalize.  Increasing the exposure by 0.3 EV (1/20 s, f/8) causes clipping on the camera histogram and the raw histogram is slightly clipped in the green channel (vertical dotted line indicates clipping). The camera histogram is pretty reliable on this camera.

Not familiar with Rawnalize but would not a green clip indicate saturation clipping and not full tonal clipping until all three channels move towards a true clip?
Title: Re: Adobe RGB vs sRGB
Post by: Robert Boire on September 30, 2010, 01:23:49 pm
What difference are we talking about here? Between jpeg and RAW, or between sRGB and Adobe RGB, or...?

I was talking about the difference between jpeg and RAW with an Adobe RGB color space. Again comparing the two against each other on the computer monitor and the jpeg on the camera LCD, I did not see much of a differnce.

On the other hand my sample was small and referring to
Now read the article here on Expose to the Right, then actually test that. What you’ll see is that ETTR with proper “normalization” settings in the converter now produces a preview that matches the JPEG yet you “over exposed” (some would suggest properly expose) the raw data. And the matching JPEG with the same raw exposure? Its way blown out. There’s a really big disconnect between the raw data and the JPEG when you capture the raw data for raw (not JPEG) exposure.


I admit that several of the shots I was looking at had very subdued lighting and little contrast and no highlights to speak of, so I will do my homwork and read the ETTR article.
Title: Re: Adobe RGB vs sRGB
Post by: bjanes on October 01, 2010, 01:30:32 pm
Not familiar with Rawnalize but would not a green clip indicate saturation clipping and not full tonal clipping until all three channels move towards a true clip?

Rawnalyze is a freeware program that looks at the raw data directly without demosaicing, white balance, or other processing. Unfortunately, the author has passed away and I don't know if the program is currently available on line. The use of the tool is briefly discussed in this Libraw aricle (http://www.libraw.org/articles/white-balance-in-digital-cameras.html) which deals with white balance.

The examples I showed deal with clipping in the green channel with intact red and blue channels. Of course, if white balance is applied, the channels would clip more or less equally. As you know, the green channel usually clips first with most cameras and most illuminants.  Personally, I try to avoid clipping in any channel. Although highlight recovery is useful, the colors may not accurate.

Bill
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 01, 2010, 01:35:58 pm
The examples I showed deal with clipping in the green channel with intact red and blue channels. Of course, if white balance is applied, the channels would clip more or less equally. As you know, the green channel usually clips first with most cameras and most illuminants.  Personally, I try to avoid clipping in any channel. Although highlight recovery is useful, the colors may not accurate

Understood. But in the context of the “clippies” we see on the LCD versus the actual tone clipping of the raw data, would we not have to increase the exposure of the raw a bit more to produce an apples to apples comparison?

My original point is, 1-1.5 stops past initial clipping seen on my LCD provides a raw that, at least in LR and ACR can be adjusted such that there is no clipping (getting back to “Pardon my ignorance, but isn't "a huge stretch" a huge stretch“?).
Title: Re: Adobe RGB vs sRGB
Post by: Daniel Browning on October 03, 2010, 11:09:48 pm
Unfortunately, the author has passed away and I don't know if the program is currently available on line.

It is available here:

http://dave-anderson-photo.com/blog/2010/08/23/gabor-rawnalyze-author-rip/
Title: Re: Adobe RGB vs sRGB
Post by: eliedinur on October 04, 2010, 08:48:40 am
I was talking about the difference between jpeg and RAW with an Adobe RGB color space. Again comparing the two against each other on the computer monitor and the jpeg on the camera LCD, I did not see much of a differnce.

You fail to say how you were viewing the RAW, because in fact you cannot actually view a RAW. A RAW file is not an image file. It is a collection of data that will provide the starting point for a series of operations that will in the end generate (convert to) a color image. So when you open a RAW in an image viewer one of two things has to happen - either the application does an on-the-fly generation from the RAW of a display image (which may or may not be done the same way as your camera does it when it generates a jpg) or the application is doing it the easy way and simply displaying the embedded jpg inserted into the RAW file by the camera. Obviously, in the second case the two camera-generated jpgs will be identical. So you really need to be more explicit about just what you are viewing and how.
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 04, 2010, 10:21:29 am
It is available here:
http://dave-anderson-photo.com/blog/2010/08/23/gabor-rawnalyze-author-rip/

My god, I had no idea we lost panopeeper who was a regular presence here. Very sad.
Title: Re: Adobe RGB vs sRGB
Post by: Mark Paulson on October 04, 2010, 12:00:33 pm
The camera histogram is pretty reliable on this camera.

I have experimented with UniWB and one thing I discovered is that the Nikon picture control and some of the other setting can greatly affect the histogram. I do not use UniWB anymore , but I found that zeroing out and turning off all of the thing on the D3 that have an effect on exposure allows me to get maximum exposure without clipping the RAW data. I generally can get 0.5 to 1.0 stop more exposure.
Title: Re: Adobe RGB vs sRGB
Post by: JeffKohn on October 04, 2010, 04:26:44 pm
I have experimented with UniWB and one thing I discovered is that the Nikon picture control and some of the other setting can greatly affect the histogram. I do not use UniWB anymore , but I found that zeroing out and turning off all of the thing on the D3 that have an effect on exposure allows me to get maximum exposure without clipping the RAW data. I generally can get 0.5 to 1.0 stop more exposure.
Yes, agreed. I've found that for all the Nikon DSLR's I've used, using the "neutral" picture control with a flat tone-curve, Adobe RGB colorspace, and UniWB will result in the camera histogram being a pretty accurate representation of the raw data (within about 1/3 stop or so).

It's true that if you crank up the various in-camera settings so that the preview has more "pop", the histogram won't be as accurate. But I'm not sure why you would ever do that if you're shooting raw and care about histogram accuracy.
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 04, 2010, 04:29:35 pm
Yes, agreed. I've found that for all the Nikon DSLR's I've used, using the "neutral" picture control with a flat tone-curve, Adobe RGB colorspace, and UniWB will result in the camera histogram being a pretty accurate representation of the raw data (within about 1/3 stop or so).

Accurate for JPEG or accurate for the linear raw data, (exposing for the best raw data ETTR)? That’s the $64K question.
Title: Re: Adobe RGB vs sRGB
Post by: bjanes on October 04, 2010, 09:03:59 pm
Yes, agreed. I've found that for all the Nikon DSLR's I've used, using the "neutral" picture control with a flat tone-curve, Adobe RGB colorspace, and UniWB will result in the camera histogram being a pretty accurate representation of the raw data (within about 1/3 stop or so).

It's true that if you crank up the various in-camera settings so that the preview has more "pop", the histogram won't be as accurate. But I'm not sure why you would ever do that if you're shooting raw and care about histogram accuracy.

I keep near UniWB supplied by Iliah Borg in Bank 4 on my D3. Usually the green blows first with normal WB, but with high saturation red or blue subjects, the red or blue channels may show saturation clipping after white balance and one can use UniWB to determine if the clipping was caused by white balance or WB multipliers > 1.0 in those channels or by clipping in the raw channels. However, I don't use UniWB that much.

True UniWB didn't work with previous versions of ACR, and I don't know if that limitation is present with the current version.

Regards,

Bill

Title: Re: Adobe RGB vs sRGB
Post by: Mark Paulson on October 05, 2010, 12:16:03 pm
Accurate for JPEG or accurate for the linear raw data, (exposing for the best raw data ETTR)? That’s the $64K question.

Accurate for RAW not JPEG. If you actually use UniWB to set the for WB then you will hardly ever blow any of the data. If you don't use it and zero out everything else. you can still get pretty close without blowing a channel by backing off a little from the right.
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 05, 2010, 03:20:02 pm
Accurate for RAW not JPEG. If you actually use UniWB to set the for WB then you will hardly ever blow any of the data. If you don't use it and zero out everything else. you can still get pretty close without blowing a channel by backing off a little from the right.

I don’t understand how the UniWB has anything to do with exposure. WB for raw is just a metadata suggestion anyway. Can you clarify the workflow?
Title: Re: Adobe RGB vs sRGB
Post by: JeffKohn on October 05, 2010, 04:15:19 pm
I don’t understand how the UniWB has anything to do with exposure. WB for raw is just a metadata suggestion anyway. Can you clarify the workflow?
The point of UniWB is that it makes the in-camera histogram more accurate because no WB coefficients are applied to the R/B channels. So you can see the actual exposure for those channels rather than being mislead by WB adjustments that may indicate a channel is clipped when it really isn't.

With UniWB and neutral/flat picture controls, I find the in-camera histogram to correlate quite well with the histogram in ACR. It's still gamma-corrected, of course; but it you don't need a linear histogram to judge exposure.
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 05, 2010, 04:19:37 pm
The point of UniWB is that it makes the in-camera histogram more accurate because no WB coefficients are applied to the R/B channels.
Accurate for what? ETTR? The proper exposure for the JPEG? I’m confused.

Quote
So you can the actual exposure for those channels rather than being mislead by WB adjustments that may indicate a channel is clipped when it really isn't.

But how does this have anything to do with the raw data? I can take an incident reading, open up a good stop plus, shoot raw and completely bring in the clipping seen with the default raw rendering (or what the camera would obviously show as clipping of the JPEG) due to ETTR (all that actual data in the highlights that didn’t really clip). I could see how this tool would produce a better idea of clipping and exposure for JPEG. I still don’t see how a histogram and an exposure based on a gamma corrected JPEG correlates to the raw data based on a rendering setting (of the Exposure slider) it can’t possibly know exists.
Title: Re: Adobe RGB vs sRGB
Post by: JeffKohn on October 05, 2010, 05:05:34 pm
Andrew I'm not really sure how else to explain it, I think you're over-complicating things. The fact that the camera histogram is not linear doesn't really matter. The histogram in ACR isn't linear either.

All I'm saying is that with UniWB, flat tone curve, Adobe RGB colorspace, and other "neutral" in-camera settings, the in-camera histogram will be a pretty close match for what I would see opening the RAW file in ACR with default settings. The in-camera histogram will still be slightly pessimistic, showing clipping about 1/2 stop before the raw data is actually clipped.  But for ETTR I would rather have the highlights a hair below clipping as opposed to having even one channel clip.

Bill's point was that the green channel is almost always the first one to clip anyway, so UniWB isn't all that necessary. That's mostly true in the general case; but if shooting a subject where the red or blue channel is strongly saturated (flowers, for instance), UniWB can be useful. It's also useful if you're using a magenta filter to 'cut' the green channel and equalize it relative to the red and blue channels. Since I never shoot JPEG I tend to just leave UniWB on all the time.

Title: Re: Adobe RGB vs sRGB
Post by: JeffKohn on October 05, 2010, 05:07:18 pm
Quote
True UniWB didn't work with previous versions of ACR, and I don't know if that limitation is present with the current version.
You may be right, to be honest I can't remember if the WB setting I got from Iliah was true UniWB or "near". The difference is negligible as far as judging exposure goes.
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 05, 2010, 05:28:12 pm
The fact that the camera histogram is not linear doesn't really matter. The histogram in ACR isn't linear either.
No and neither is the data at this point. But more importantly, the ACR histogram shows you the raw data based on the current rendering settings. The histogram on the LCD shows you the JPEG rendering. If I expose such that the JPEG shows severe clipping, the clipping totally disappears in ACR, from the raw when I update the rendering for exposure (as does the clipping in the ACR Histogram).

I still can’t see how anything you do in front of or with the camera that affects the JPEG reporting on the LCD tell you the facts about the raw.
Title: Re: Adobe RGB vs sRGB
Post by: JeffKohn on October 05, 2010, 06:09:53 pm
Quote
If I expose such that the JPEG shows severe clipping, the clipping totally disappears in ACR, from the raw when I update the rendering for exposure (as does the clipping in the ACR Histogram).
I guess we're just talking past each other at this point. I don't know what you mean by "when I update the rendering for exposure". Are you saying that your images typically show clipping in ACR until you use a negative adjustment on the exposure slider? The fact that you can eliminate the clipping indicators in ACR with a negative exposure adjustment does not mean that your raw data wasn't clipped.

Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 05, 2010, 06:39:25 pm
I don't know what you mean by "when I update the rendering for exposure". Are you saying that your images typically show clipping in ACR until you use a negative adjustment on the exposure slider?

Yes, exactly. Yet there is no clipping based on this ETTR exposure to the raw data. There is clipping if I shot JPEG (or raw+JPEG) on said JPEG. IOW, the optimum exposure to avoid clipping is significantly different for a JPEG than a raw and hence I can’t see how working with controls on a camera that tells us something about the JPEG can correlate to the raw.
Title: Re: Adobe RGB vs sRGB
Post by: bjanes on October 05, 2010, 07:06:47 pm
Yes, exactly. Yet there is no clipping based on this ETTR exposure to the raw data. There is clipping if I shot JPEG (or raw+JPEG) on said JPEG. IOW, the optimum exposure to avoid clipping is significantly different for a JPEG than a raw and hence I can’t see how working with controls on a camera that tells us something about the JPEG can correlate to the raw.

Andrew and Jeff,

I think that this example can clarify the issue. This image was shot with the Nikon D3 under daylight using the standard picture control (neutral) and Adobe RGB (the widest space on this camera). My initial shot showed clipping on the camera RGB histogram in the green and red channels, so I decreased exposure until there was no green clipping. I didn't have UniWb at the time.

The camera histogram and the raw histogram as shown by Rawnalize are shown.  The camera histogram shows clipping in the red and green channels. The green might not clip in ProPhotoRGB, but that is not an option with this camera. The raw histogram shows that the red channel is more than 1/3 stop below clipping. However, the red multiplier for white balance for this channel is 1.6992. When this is applied, the red will be clipped. If I were using UniWB, I could have seen that the red channel was short of clipping and inferred that the clipping took place with white balance.

 

Title: Re: Adobe RGB vs sRGB
Post by: Robert Boire on October 05, 2010, 10:37:48 pm
 OK, so I most admit the last several posts on UniWB were a bit esoteric (at least for me) but I''m back to one of my original questions. I understand that sRGB is preferred for the Web, but I am not clear why. Is because the monitors that most people use support only sRGB or is there something else.
Title: Re: Adobe RGB vs sRGB
Post by: JeffKohn on October 05, 2010, 11:05:17 pm
OK, so I most admit the last several posts on UniWB were a bit esoteric (at least for me) but I''m back to one of my original questions. I understand that sRGB is preferred for the Web, but I am not clear why. Is because the monitors that most people use support only sRGB or is there something else.
It's because many if not most people are surfing the web with browsers that treat all images as if they were sRGB.  When a browser displays a non-sRGB image as if it were sRGB, the result can look pretty bad (particularly for Pro Photo RGB).
Title: Re: Adobe RGB vs sRGB
Post by: Robert Boire on October 05, 2010, 11:16:09 pm
So it has nothing to do with the monitor but the application?

Meaning, for example, if I am showing a "slide" show on my monitor using an application that understands what color space the image is in (like Photoshop does), then the result should be ok? ???
Title: Re: Adobe RGB vs sRGB
Post by: Slobodan Blagojevic on October 06, 2010, 12:10:14 am
A brief introduction to sRGB vs. Adobe RGB can be found here:

http://www.cambridgeincolour.com/tutorials/sRGB-AdobeRGB1998.htm
Title: Re: Adobe RGB vs sRGB
Post by: ErikKaffehr on October 06, 2010, 12:11:45 am
Hi,

Yes, if you can find one and if your images are correctly tagged. The monitor should naturally be properly calibrated.

Adobe RGB and sRGB are pretty close, even if Adobe RGB primaries stretch farther in the blue greens. You can probably get away with showing Adobe RGB on an sRGB system even without correctly handling profiles. Prophoto RGB is another matter, it will be obviously bad.

That is actually an advantage with Prophoto RGB, it's obvious when wrong!
My 2 cents:

- If you have an Adobe RGB capable monitor use Adobe RGB
- If colors fall into sRGB than choice of RGB will not matter, but it may be that you get better tonal separation in sRGB
- Use ProphotoRGB as working space, this way you will not throw away colors that would be outside sRGB or Adobe RGB
- Export to sRGB if you are not absolutely sure that the recipient knows what he/she is doing

Best regards
Erik


So it has nothing to do with the monitor but the application?

Meaning, for example, if I am showing a "slide" show on my monitor using an application that understands what color space the image is in (like Photoshop does), then the result should be ok? ???

Title: Re: Adobe RGB vs sRGB
Post by: eliedinur on October 06, 2010, 08:01:50 am
So it has nothing to do with the monitor but the application?

No, it has to do with the monitor also. The sRGB space was created in 1996 by Microsoft and HP and designed to represent the native space of a theoretical "average" monitor in use at that time. There were deviations of course, but sRGB would be the "golden mean". Despite the fact that there are today many "wide gamut" monitors in the market, the large majority continue to be reasonably close to the sRGB model. Thus, if the image data is in sRGB, when it is passed through to most monitors without any alteration by a non-c.m. browser the display may not be accurate but it will be acceptable.
Title: Re: Adobe RGB vs sRGB
Post by: Sheldon N on October 06, 2010, 11:17:30 pm
As someone else said early on in the thread, it really boils down to individual need and usage.
A little goody I came across,  from the horses mouth ...


http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf

Are you calling Andrew Rodney a horse? LOL :)  

He's the author of that article, and has already posted to this thread several times (User ID digitaldog).
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 07, 2010, 10:28:22 am
A little goody I came across,  from the horses mouth ...

From the dogs mouth <g>
Title: Re: Adobe RGB vs sRGB
Post by: hjulenissen on October 28, 2010, 02:44:36 am
Did anyone mention that sRGB has an advantage over Adobe RGB when it comes to banding?

-h
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 28, 2010, 11:58:12 am
Did anyone mention that sRGB has an advantage over Adobe RGB when it comes to banding?

An advantage, how so?
Title: Re: Adobe RGB vs sRGB
Post by: Schewe on October 28, 2010, 12:07:03 pm
Did anyone mention that sRGB has an advantage over Adobe RGB when it comes to banding?

If you have proof that the same image in sRGB bands less than the image in Adobe RGB with the same processing, I would like to see it...

A lot of people talk about the "efficiency" of a color space being important. To date, I've never actually seen proof. I've been using Pro Photo RGB since Bruce Fraser talked me into doing so in early 2001 (the only caveat is I also only use 16 bit). I've never seen banding that could be attributed to having used an inefficient color space. I have however seen banding introduced because 8 bits simply were not enough-regardless of the color space the image was in.
Title: Re: Adobe RGB vs sRGB
Post by: hjulenissen on October 28, 2010, 02:51:04 pm
An advantage, how so?
I did not investigate this my self, but the argument is often heard, and seems reasonable: if you stretch 8 bits over a larger distance, each step will be larger.

That is, of course, assuming that one is limited to 8/24bpp.
http://www.earthboundlight.com/phototips/srgb-versus-adobe-rgb-debate.html
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 28, 2010, 02:52:52 pm
if you stretch 8 bits over a larger distance, each step will be larger.

But I don’t stretch 8-bits per color nor recommend anyone do so.
Title: Re: Adobe RGB vs sRGB
Post by: hjulenissen on October 28, 2010, 02:56:10 pm
But I don’t stretch 8-bits per color nor recommend anyone do so.
It was my understanding that the threadstarter was asking about sRGB/Adobe RGB formats out of his Canon camera?
...
I know that Adobe has a wider gamut than sRGB. However are their situations when sRGB is in fact preferred?

I ask because my Canon user manual states "Adobe RGB is not recommended if you do not know about image processing, Adobe RGB and Design Rule for Camera File System 2.0", which in fact pretty much tells me nothing at all...
Title: Re: Adobe RGB vs sRGB
Post by: digitaldog on October 28, 2010, 02:59:30 pm
It was my understanding that the threadstarter was asking about sRGB/Adobe RGB formats out of his Canon camera?

His camera captures raw which is neither of those color spaces nor is it 8-bits per color. He wrote:
Quote
I know that Adobe has a wider gamut than sRGB. However are their situations when sRGB is in fact preferred?
I ask because my Canon user manual states "Adobe RGB is not recommended if you do not know about image processing, Adobe RGB and Design Rule for Camera File System 2.0", which in fact pretty much tells me nothing at all.

And then he stated:
Quote
In fact I have been shooting RAW recently.
Title: Re: Adobe RGB vs sRGB
Post by: Schewe on October 28, 2010, 05:18:33 pm
I did not investigate this my self, but the argument is often heard, and seems reasonable: if you stretch 8 bits over a larger distance, each step will be larger.

That is, of course, assuming that one is limited to 8/24bpp.
http://www.earthboundlight.com/phototips/srgb-versus-adobe-rgb-debate.html

I read the article...it only goes along with the myth and offers no PROOF that Adobe RGB is any more prone to banding than sRGB. So, until I see some actual proof that Adobe RGB is more prone to banding, I think I'll file this under "it's an old wives tale" rather than proven fact. Heck, I've even played with 8 bit ProPhoto RGB files to try to make them band...and you can if you apply outrageous adjustments to the file but the same adjustments will cause banding in sRGB and Adobe RGB as well. Working in 16 bit (actually, 15 bit plus 1 level) eliminates the need to worry about banding.
Title: Re: Adobe RGB vs sRGB
Post by: hjulenissen on October 29, 2010, 03:36:11 am
Working in 16 bit (actually, 15 bit plus 1 level) eliminates the need to worry about banding.
Agreed, If that is possible.

However, if you want to use JPEGs out of a camera, you usually have the choice between 8-bit sRGB and 8-bit Adobe RGB (further losses introduced by matrixing, color subsampling and JPEG). Most people that are really into precision will probably use raw, but there are some scenarios where one might have to use JPEG (if maximum sustained fps is important, or maximum available storage)

-h
Title: Re: Adobe RGB vs sRGB
Post by: jbrembat on October 29, 2010, 05:02:17 am
Abobe RGB 1998 is a  color space larger than sRGB.
Using the same bit depth, in Adobe RGB 1998 a color step is stronger.
That does'nt require a proof.
So, theoretically speaking, Adobe RGB 1998 is more prone to banding than sRGB.

But, in practice, you have to evaluate if banding is visible.
Banding visibility is related to noise level too.

Generally, a good editing (not an extreme one) doesn't generate banding in any color space.

Jacopo