App that quantifies the relation between two colors?

#1

Greetings,

I’m helping a child out with a project and need some assistance.

I’m fully aware that the colors on my monitor won’t be the same when printed from my home printer and the reasons why, but we’re still trying to get the colors as close as possible to the color on the screen. The monitor is calibrated. After some experimenting I’ve come across a color that prints close enough. There are a few other colors to replicate and I’m hoping now that I’ve figured out the values of the monitor and printer versions of this color that I can replicate the remaining colors in an easier manner than trial-by-error.

Does anyone know of an app where it would be possible to enter the HEX, RGB, CMYK codes of the two colors that can determine a mathematical relation that can be applied to another color to determine the value of X (the unknown color). Like simple math solving for X using cross multiplication - if I know the relation between A/B, then I should be able to calculate the relation between C/X.

Open to any ideas, apps, tools, or old fashioned, manual calculations as well.

Thanks

#2

One thing that might thwart your efforts is that CMYK has a smaller gamut than RGB. Color within the gamut of both could be calculated, but those lying outside CMYK’s gamut cannot — they can only be approximated to whatever color is closest within the CMYK color space.

As for an app that will do all that, plus compensate for the gamut differences, doesn’t Photoshop’s algorithms and various color and output device settings already do that when converting from RGB to CMYK?

Perhaps I’m misunderstanding what you’re asking.

#3

Thanks for the reply. Sorry if I was unclear.

I’m far from being an expert, but I get what you’re saying as far as printers having a smaller gamut. I’m not familiar enough with the workings of Photoshop to know how exactly the algorithms function.

Here’re the details:

We’re trying to come up with a printed color that looks close enough to Pantone Olive Oil:

RGB 173 141 48

HEX/HTML AD8D30

“CMYK values not available” (says the Pantone website, but when entered into Photoshop = 32 40 100 6)

After trial and error I came up with a color that prints out close enough:

RGB 198 198 42

HEX/HTML c6c62a

CMYK 27 11 100 0

I’ve tried printing using rendering intent: perceptual, saturation, and relative colormetric and set color management to where Photoshop manages colors using my printer’s profile.

Given the above information, I’d like to know if there’s a way to quantify what the difference between the colors are so that I can use that formula to figure out how to approximate another color without having to go through all the trial and error.

Obviously, I’m not knowledgeable of exactly how color codes work beyond a very basic understanding. I get the larger theory, but know nothing of the details. Is it as simple as adding/subtracting the differences between the RGB values of the colors I’ve already semi-matched to a different color I’m trying to match and then let Photoshop convert for CMYK? That would seem too simple, but I truly don’t know. It’d be great if there was an existing app I could plug codes into, like the basic math equations with fractions solving for the unknown x, but I’m fine with a manual calculation. Just would like to know if there’s a discernible and quantifiable relation that exists that can be calculated using any of the three color codes and then use that knowledge of the relation between colors A and B to determine the relation between colors C and X.

I hope I’ve been clearer. Thanks again.

#4

Since nothing beats a failure but a try, I took another Pantone color (Cayenne), added/subtracted the differences from my Pantone Olive Oil and the semi-matched color. The difference was nowhere near the same and the printed results of the actual colors were much closer to what my monitor shows. Assuming that Cayenne is within my printer’s gamut while Olive Oil is not.

Another thing I might try is duplicating and using a proof and applying a curve to brighten up the mid-levels.

Still curious if there’s an app or way to manually calculate what I posted looking for re: a mathematical formula to calculate the differences between two colors whose relation can be applied to other colors.

#5

AD8D30 is a very different color from C6V62A. If the second hex value color matches your first hex value on your printer’s output, that speaks more to the accuracy of your printer than anything else.

Home printers will never accurately reproduce colors, and the output differs enormously from one model to the next. Even high-end proofing machines costing thousands of dollars don’t get the colors perfectly (close but not perfect).

For what it’s worth, the numerical values you gave me don’t match up from RGB to HEX to CMYK in my version of Photoshop. Apparently, Adobe continues to tweak their algorithms to better approximate colors when moving from an additive to a subtractive color environment. For that matter, seeing CMYK colors on a monitor is only an approximation of what those colors will look like in the additive color space of a display. Also Pantone CMYK equivalents of their spot colors don’t match up with what Adobe says those equivalents are, which probably says something about the difficulty of reducing these conversions to simple algorithms.

There’s no magic formula for this because it’s a bit like comparing apples to oranges with a million inconsistent variables thrown into the mix. As for an app, like I mentioned Photoshop already does these things. Even the color picker will show you approximate equivalents of CMYK, HEX and RGB. As you’ve found, though, these approximations make little difference to your home printer that isn’t accurate enough to print them.

#6

Thanks for your input and help.

By the way. The color that I got to match somewhat with Pantone Olive Oil was c6c62a, not c6v62a which is a very deep blue and far from the greenish yellow of c6c62a. After initial disappointment, the kid is fine with our close enough approximation and now understands that what you see on the monitor isn’t exactly what comes out of the printer.

#7

I apparently hit the V instead of the C when I typed it in here. I did look at C6C62A on my monitor and saw the colors were quite different — similar in chroma, but lighter and skewed toward yellow.

Hexadecimal only uses 16 numerical symbols: 0 through F . There is no V in hex.

As you’ve noticed, color matching is full of pitfalls. I wish it were a bit more straight-forward, but it isn’t. :wink:

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