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Author Topic: Adobe RGB vs sRGB  (Read 10847 times)
RobertBoire
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« on: September 26, 2010, 11:25:48 AM »
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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
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Slobodan Blagojevic
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« Reply #1 on: September 26, 2010, 12:25:36 PM »
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...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.




« Last Edit: September 26, 2010, 07:02:43 PM by Slobodan Blagojevic » Logged

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digitaldog
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« Reply #2 on: September 26, 2010, 02:10:16 PM »
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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.
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Andrew Rodney
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RobertBoire
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« Reply #3 on: September 26, 2010, 06:59:05 PM »
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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?
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digitaldog
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« Reply #4 on: September 26, 2010, 08:17:54 PM »
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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.
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Andrew Rodney
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RobertBoire
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« Reply #5 on: September 26, 2010, 08:50:17 PM »
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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
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Slobodan Blagojevic
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« Reply #6 on: September 26, 2010, 08:52:45 PM »
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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.

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

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

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... 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.
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Slobodan Blagojevic
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« Reply #7 on: September 26, 2010, 09:14:10 PM »
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... 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?
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« Reply #8 on: September 26, 2010, 09:37:35 PM »
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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.
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bjanes
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« Reply #9 on: September 27, 2010, 06:29:36 AM »
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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
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stamper
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« Reply #10 on: September 27, 2010, 07:05:34 AM »
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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?
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bjanes
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« Reply #11 on: September 27, 2010, 07:43:42 AM »
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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
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Slobodan Blagojevic
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« Reply #12 on: September 27, 2010, 12:01:31 PM »
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... 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.
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Slobodan

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digitaldog
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« Reply #13 on: September 28, 2010, 02:32:59 PM »
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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.
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Andrew Rodney
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RobertBoire
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« Reply #14 on: September 29, 2010, 08:23:45 PM »
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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?
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digitaldog
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« Reply #15 on: September 30, 2010, 08:53:05 AM »
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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.
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Andrew Rodney
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Slobodan Blagojevic
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« Reply #16 on: September 30, 2010, 09:20:09 AM »
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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...?
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Slobodan

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bjanes
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« Reply #17 on: September 30, 2010, 09:31:58 AM »
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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.

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stamper
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« Reply #18 on: September 30, 2010, 10:13:06 AM »
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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? Roll Eyes
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digitaldog
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« Reply #19 on: September 30, 2010, 10:23:54 AM »
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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?
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Andrew Rodney
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