Converting color spaces

[RedRebel]

I just have a brief question...

When I create a document in sRGB and convert it to AdobeRGB1998, does the appearance on my monitor stay the same?

I see that the color numbers change (I created a test chart Babelcolor) that is logical since Adobe RGB has a larger colour space, so the colours are remapped to the new colorspace. But I would expect that if the color management works right, the result on the monitor looks the same. I don't expect this for colors that are out of the sRGB gamut, but not for simple sRGB colors.

...or do I mis something? ...must be

My Proof setup is Monitor RGB and I enabled proof colors.

[paulbk]

In general, Proof Colors is for previewing output, in other words, the print. Use proof setup to select the proper printer & paper OUTPUT profile to see what the print will look like (sorta). Since Photoshop is color management enabled, all screen output (everything you see on screen) is seen through your working color space and the monitor profile (if you have one).

[PeterLange]

I just have a brief question...

When I create a document in sRGB and convert it to AdobeRGB1998, does the appearance on my monitor stay the same?

Yes - unless you do this:

My Proof setup is Monitor RGB and I enabled proof colors.

With Softproof 'Monitor RGB' the 'preserve color numbers' function is automatically enabled. It mimics a non-icc-aware application.

Peter

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[Mark D Segal]

I don't understand why you would want your proof set-up to be Monitor RGB, unless you are not editing for eventual printing. If you are editing for printing your soft proof set-up should contain the output profile for your printer. Furthermore, if you create a document in sRGB, there is no more data to be had, so converting it to Adobe RGB98 buys you nothing.

[digitaldog]

Different color numbers can and often do produce the same color appearance. You saw that in the sRGB and Adobe RGB tests done. As you point out, this is logical, the scale of the numbers are different (different color spaces) but the color is the same appearance.

Monitor RGB doesn't bring ANYTHING to the party but show you how that image will appear outside smart ICC aware applications on THAT ONE machine. It doesn't show you how that image will appear outside a smart ICC aware application on anyone else's machine (without color management, a display profile for example, that's impossible). So Monitor RGB isn't very useful.

[RedRebel]

Ok sory I made a mistake.

I was making Gretag Macbeth colorchecker card in sRGB, AdobeRGB and ProPhoto, using Photoshop and comparing them the wrong way, using the wrong RGB values in the wrong colorspace and I thougt enabling Proof Colors would solve the thing but it didn't.

The right way I did it now:
- Create a color checker card in sRGB using the values from the BabelColor website. I used the "sRGB" values specified in the top table on page 5.
- Then I converted this 'original' file using Photoshops 'Convert to profile' function to create an Adobe RGB and a ProPhoto document.

When I open these three documents in Photoshop and I compare the colors visualy (on my simple monitor, without enabeling Proof Colors) then they look identical. When I use the eyedropper tool to get the RGB values I notice that the values are almost identical to the values specified for AdobeRGB and ProPhoto in the same table on page 5. The small differences are likely caused by rounding erors. The values usual differ only +/- 1 except for the values that are clipped eg. cyan.

It's an useless experiment   , the only thing it learnd me are:
- a specific color has different RGB values in different color spaces
- converting a document from one color space to another doesn't change the apearance from an image as long as the colors are within the Gamut from the respective color spaces...sRGB, AdobeRGB and ProPoto.
- converting color space leads to (small) rounding erors.
- Photoshops color picker seems to be 8 bit, since I can only specify CIE LAB values like 38; 14; 14 and not 37,99; 13,56; 14,06
- there's still a lot to learn  

It takes to long for this thread, but for the ones that are interested in ColorChecker RGB numbers, ColorChecker acuracy and tranformations from one to the other color spaces should have a look at BabelColor

The atached image is an sRGB image using the sRGB (not the sRGB (GMB) ) values from the top table on page 5 form the Babelcolor pdf. If you wan't to check your own GretagMacbeth color checker you should use the values specified by GretagMacbeth (table sRGB(GMB)) or the averaged values from BabelColor in the lower table on page 5.

[PeterLange]

The right way I did it now:
- Create a color checker card in sRGB using the values from the BabelColor website. I used the "sRGB" values specified in the top table on page 5.
- Then I converted this 'original' file using Photoshops 'Convert to profile' function to create an Adobe RGB and a ProPhoto document.

BabelColor as well as Colorremedies offer the simulated ColorChecker for download:

http://www.babelcolor.com/main_level/ColorChecker.htm
http://www.colorremedies.com/realworldcolor/downloads.html

Peter

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[RedRebel]

Thanks Peter, the Colorremedies site was new to me!

Yesterday I ordered an original GretagMacbeth colorchecker chart to verify my calibrations, or at least to get an idea what to expect.