RBG to CMYK Conversion Chart

MM
Posted By
Mac McDougald
Jun 26, 2003
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1062
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14
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Closed
Not to mention that there are 16.7 *million* colors possible in RGB. That would be some long "chart" πŸ™‚

Mac

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MM
Mac McDougald
Jun 26, 2003
Not to mention that there are 16.7 *million* colors possible in RGB. That would be some long "chart" πŸ™‚

Mac
P
Phosphor
Jun 26, 2003
Nancy,

You can find the CMYK color corresponding to any RGB color, as used by Adobe PS, by going to the Adobe color picker and reading the component values, which are shown for both systems, as well as for HSB.

George
P
Phosphor
Jun 26, 2003
Nancy,

You can find the CMYK color corresponding to any RGB color, as used by Adobe PS, by going to the Adobe color picker and reading the component values, which are shown for both systems, as well as for HSB.

George
JR
John R Nielsen
Jun 27, 2003
But, again, the results will vary with your color settings.
R
Roberto
Jun 27, 2003
You can find the CMYK color corresponding to any RGB color, as used by Adobe PS, by going to the Adobe color picker and reading the component values, which are shown for both systems, as well as for HSB.

Keeping in mind, of course, that there is no one single CMYK formula for any given RGB value; how Photoshop converts from any three-color mode (RGB, Lab) to CMYK is dependent on your CMYK settings or color profile.

Brian
BC
bart.cross
Jun 27, 2003
There is no ‘free’ when it comes to this. To make sure I get the right CMYK values I use my Pantone Survival Books. That way you can work blind (although I have a colour corrected system specifically for CMYK), if necessary, and know what will come off a press.

Lastly, what is ‘right’ is in the eye of the beholder and you will never satisfy everyone.

You may want to start here: < http://www.pantone.com/support/support.asp?idArticle=73& platform=PC>
P
Phosphor
Jun 27, 2003
"…But, again, the results will vary with your color settings…"

John, I’m thinking that the color setting variations could be circumvented by relating the RGB and CMYK values to Lab values, which are also given by the color picker and are device independent.

George
MM
Mac McDougald
Jun 27, 2003
In article , says…
"Not to mention that there are 16.7 *million* colors possible in RGB" At that’s just for RGB images at 8 bits per channel.

Not that we can perceive the diffs between more than maybe 25% of the 16.7.

It’s often stated that we also can’t see the diffs between more than about half of a 256 step grayscale wedge.

In both cases we can *see* all the gradations, just can’t perceive the diffs between one and the one next to it (or the one next to next to it) and etc.

Mac
P
Phosphor
Jun 27, 2003
"…Not that we can perceive the diffs between more than maybe 25% of the 16.7"

My compliments to you, Mac! 25 colors rather than 25% of 16.7 million colors would be closer to the truth, at least for my myopic eyes.

The reason 256 tonal variations in each color channel are used (and even that is not enough) is not at all because the eye-brain can distinguish anywhere near that number. Non-linear device responses, digital quantization, and the need to exaggerate contrasts in selected portions of the full tonal range to bring out otherwise hidden (to the eye) detail are the reasons 8 bits (256 tones) per channel barely hack it and why there is so much impetus to go to 16 bits.

16 bits in 3 channels gives you 2.8 x 10^14 "colors". Better start your eye exercises in preparation for the future 16-bit color technology!!

George
MM
Mac McDougald
Jun 27, 2003
Well, monitors can’t see it and printers can’t print it, so how can my eyes perceive it? πŸ™‚

Mac
P
Phosphor
Jun 27, 2003
Mac,

With them eyes, ya shoulda taken up baseball!!

George
MM
Mac McDougald
Jun 28, 2003
George, I *could* hit a ball, but slow and flatfooted.
Had to bang em of the fence to make comfy singles πŸ™‚

Mac
GH
Gernot Hoffmann
Jun 28, 2003
The sRGB color space in CieLab doesnΒ΄t contain much more than 70.000 colors which differ by at least deltaE=1 (was counted).

In isolated tests with facing patches we can certainly distinguish some more colors.
A larger RGB color space delivers also more colors, because the human gamut in CieLab is not a closed volume but an open cone.

The maximal sum of relevant colors is perhaps in the combined volume of a monitor space, a working space and an optimal CMYK space.
A very crude estimation: all colors in Cielab are in a sphere with radius 50 in a deltaE=1 grid. This would deliver about 150.000 distinguishable colors.

Best regards –Gernot
GH
Gernot Hoffmann
Jun 28, 2003
I wonder how the scientists had tested a couple of people whether they can distinguish 5 million colors.
In fact a good idea for a 5-years research program, a little boring , though.

This reminds me of a research program where the readability of text on backgrounds was tested, but the text and the backgrounds were just the 6 primaries and secondaries (plus white and black), which are normally not used in graphics design.
They had forgotten to take into account the other 256^3 – 8 colors.

Best regards –Gernot

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