Colour Space(s)

[petercook80]

Hi, I dont wish to start (or re-start) the Adobe RGB v sRGB debate but one thing puzzles me that I can't seem to google an answer for and that is this.

If I am viewing on a monitor that covers about 97% sRGB and 76% Adobe RGB (which is usual for a good decent monitor without moving up to the expensive wide gamut monitors - mine is a Dell U2312HM) how could I see the differences in using Adobe RGB?
If my monitor can't reproduce all the colours in Adobe RGB and I use it anyway what happens to the colours that my monitor can't reproduce?

I have always used Adobe RGB, but when investigating specs for my new monitor and ending up with the Dell this thought occurred to me.

(as a note I use a i1 Display 2 to profile my monitor and I use custom printer profiles as well. I am not new to this game but this is a question that I have unable to find an answer)

Any answers to this specific question would be appreciated as it will help expand my understanding.

[fdisilvestro]

If my monitor can't reproduce all the colours in Adobe RGB and I use it anyway what happens to the colours that my monitor can't reproduce?

They will be reproduced by the closest color your monitor can reproduce, usually a less saturated color. You might lose texture details.

If you have a very saturated green which is inside AdobeRGB but outside your monitor gamut, you'll see it as a less saturated green

[petercook80]

Okay thanks for that info.
To move on a bit , is there any benifit from using Adobe RGB or am I better off using sRGB (taking into account my monitor)

(I also suspect this applies to many many people who do not have wide gamut monitors but process in Adobe RGB or even ProPhoto)

[afx]

Use a working space that is wider than your image to ensure you do not loose anything due to clipping.
See second link in signature.

cheers
afx

[fdisilvestro]

is there any benifit from using Adobe RGB or am I better off using sRGB (taking into account my monitor)

It is always better to use a larger space, as afx suggested (as long as you don't get into combinations that might cause quantization issues like ProPhotoRGB and 8 bits).

Even if you cannot "see" those saturated colors in your monitor, you can edit them, and even bring them inside the visible gamut in a controlled way using tools like saturation or smart saturation (vibrance).

[petercook80]

Thanks for all the input.
I will carry on with Adobe RGB.  Is there any way of 'seeing' what colours (if any) in the image are being changed to suit the monitor profile (I think the Gamut Warning in PS is for printing not display  )
I am guessing there must be some way as 'FranciscoDisilvestro' susgests "Even if you cannot "see" those saturated colors in your monitor, you can edit them, and even bring them inside the visible gamut in a controlled way using tools like saturation or smart saturation (vibrance)." which makes me think that to do that you must be able to 'see' whats outside the visable gamut so you can bring them inside?

[afx]

I will carry on with Adobe RGB.  Is there any way of 'seeing' what colours (if any) in the image are being changed to suit the monitor profile (I think the Gamut Warning in PS is for printing not display  )

You can edit in a wide space and then soft proof to a small one and use the gamut alert.

I am guessing there must be some way as 'FranciscoDisilvestro' susgests "Even if you cannot "see" those saturated colors in your monitor, you can edit them, and even bring them inside the visible gamut in a controlled way using tools like saturation or smart saturation (vibrance)." which makes me think that to do that you must be able to 'see' whats outside the visable gamut so you can bring them inside?

Please read the stuff I reference in my signature. You only see approximations anyway...

cheers
afx

[petercook80]

Thanks AFX,  I did not pick up on the links in your signature even though you mentiond it (oops) I will have a read.

[petercook80]

AFX, thanks thats a great article and helps my understanding. It did not talk about ways of 'seeing' what colours are outside the ability of the monitor and are therefore being altered or is that not really worth getting worked up about?
I see you mention soft proffing and gamut alert but is that not for printing? Can you soft proof to the monitor profile when you are already viewing on the same monitor ? not sure that would work!

[fdisilvestro]

You can softproof and use gamut warning using any profile as the destination profile, not just a printing profile.

There is a limitation about Gamut Warning (at least up to Photoshop CS3, I don't know if this has changed in the newer versions): It will alert when any of the channels reach saturation or clipping (at 255) but not if it reached zero (0). Why does it matter?

Well, I found this playing with the ColorChecker. The cyan patch in the 3rd row, last column, is outside the sRGB gamut (the value of the computed R coordinate is -49), but if you use the Gamut Warning function, you will not be alerted. This is because the RGB values represented are 0; 135; 166.

Another way to analyze if there are colors outside the gamut of your monitor or desired destination space is to use 3D gamut plots. You will not be able to visualize directly which particular area of the image is out of gamut, but could give you the magnitude of the out of gamut volume. There are several tools to do this, like ColorThink Pro, up to open source combination of tools provided in Argyll CMS.

[afx]

It did not talk about ways of 'seeing' what colours are outside the ability of the monitor and are therefore being altered or is that not really worth getting worked up about?

Depends on image content. Your camera captures much more than any monitor can display.
Therefore you will never see the exact colors from the camera, but only an approximation that is as good as the monitor and the CM engines can make it.
If one needs very exact colors, this might be an issue worth looking at, but for most users this is not really relevant.

I see you mention soft proofing and gamut alert but is that not for printing? Can you soft proof to the monitor profile when you are already viewing on the same monitor ? not sure that would work!

Soft proofing is not limited to printers...
The soft proofing I mentioned in the article for screens is mostly relevant when working on a wide gamut screen and wanting to check the representation on a regular screen when images are destined for web use, so soft proofing to sRGB becomes useful.

So soft proofing to your own screen has no benefit. But, if you use gamut alerts with your screen profile, then you can show which parts of the image show approximated colors.

cheers
afx

[petercook80]

Many thanks again AFX, that last bit about Gamut Warning linked to my screens profile to show me what colours are being approximated is tha last piece in my puzzle.

I do always work in 16bit mode as well.  Now I understand it more I will switch to WideGamut (Canon DPP does not support ProPhoto and for now thats the RAW converter I use).

Thanks for all the input

Peter

[Coloreason]

... last bit about Gamut Warning linked to my screens profile to show me what colours are being approximated is tha last piece in my puzzle.
...

Try this, it may help you understand.
In Photoshop go File > New. In the new dialog window, make sure the Advanced section is expanded and for Color Profile choose Prophoto RGB and press OK. In your color panel set the RGB numbers to one of the tree primary colors for example R=255, G=0, B=0, and press Alt or Option + Delete button to fill the canvas with the selected color. Go to View > Proof Setup > Custom and from Device to Simulate menu choose the color profile of your monitor currently used by your system and make sure that Preserve RGB numbers is not checked. Then choose View > Gamut Warning and you will see the image becomes gray to show that the appearance of this color with the value R=255, G=0, B=0 in Prophoto RGB color space cannot be displayed on your monitor and the closest match is being used (approximated).

If you want to check what color values in Prophoto RGB color space are the primary colors of your monitor's color space, create an image in your monitor color space (choose your monitor profile when creating a new document) and fill it with pure red (like the example above), green, and blue. Next go to Edit > Convert to Profile and for Destination choose  Prophoto RGB. Now pick the eyedropper and measure the colors - the RGB values that you see are values in the Prophoto RGB color space corresponding to the the most saturated colors that your monitor can display. Creating more saturated colors than these values give will not make a difference on  your monitor because it can't display these colors.

[bjanes]

Another way to analyze if there are colors outside the gamut of your monitor or desired destination space is to use 3D gamut plots. You will not be able to visualize directly which particular area of the image is out of gamut, but could give you the magnitude of the out of gamut volume. There are several tools to do this, like ColorThink Pro, up to open source combination of tools provided in Argyll CMS.

One advantage of Gamutvision over the more expensive ColorThinkPro is that the former can plot a pseudocolor representation of out of gamut colors. This is not s 3D plot, but it does show the information.

Shown below is a Photoshop gamut warning and a Gamutvision plot of an image in ProPhotoRGB rendered into sRGB with relative colorimetric.

Regards,

Bill