I doubt that any of them can be translated from any R-G-B values. In short, each paint had to have it's own set of numbers to get the same color. There were even differences between the latex and oil based paints for the same brands. When I asked him if that set of numbers would work with an oil based paint he said "NO!" Each brand of paint that they carried, and they had several, needed a separate set of numbers for mixing the pigments into the base. The paint he mixed for me was the ACE brand of latex. I wanted him to record the changes that he made to a standard color that we came up with and he did. The first thing that I learned was that they did not have a sample chip that came close enough to what I wanted.īut the second thing was the real surprise. Without getting into any of the science, I recently worked with the paint guy at the local ACE hardware to get a shade that I wanted. Is unacceptable, then the trial must be corrected by adding white to make it lighter,Īdding the bluest colorant to make it bluer or less yellow, and adding the reddestĬolorant to make it redder or less green. The color is darker, greener, and yellower than the given color. L, a, b values was −0.5, −0.5, and +0.5 respectively, the trial values indicate that If the difference between the trial values and given color in L is lightness–darkness, a is redness–greenness, andī is yellowish–bluish. This transformation is simple, and all modern Meaningful visual descriptive terms and quantify color difference, the XYZ values areĬonverted into the Hunter L, a, b Scale. To facilitate the translation of the color difference from numbers to the more Differences in tristimulus values between colorsĬan be analyzed to determine the direction and magnitude of the color difference. Each color has its own tristimulus values, and These values are the amounts of three primary colors-red (X), green (Y),Īnd blue (Z)-needed to match or specify a color under illuminating and viewingĬonditions as standardized by the ICI. Get the book pdf if you care to read more.Ĭolorimeters measure color in terms of three numbers called tristimulus values. Chapter 5 "Color Matching and Color Control" (just a small paragraph). I have a book "Paint Technology Handbook" from CRC Press. Make the customer pick the color and specify it by manufacturer number. "Too blue," said the boss.ĭon't let yourself get trapped in this endless exercise. Finally after four or five tries, in desperation, he painted the drift card with his mix when he sprayed his sample, so they were both painted with the same paint. So, he'd add a bit more green, and do the whole sequence again. "Too blue," the boss would say, even though to his eye he thought he nailed it. he'd mix a batch, spray up a sample, let it dry (just a couple minutes, this was back in nitrocellulose lacquer days) and take it and the drift card into his boss. It was a teal/turquoise color and he was having a hell of a time matching it. The customer had supplied a color sample on a metal panel (often called a "drift card") for a new product they were building a model of for the early ad and catalog photos, which was common in the day. I'm reminded of a story an old time modelmaker, now recently passed on, told me years ago. Examples: highly intense purples or other secondary colors, flourescent or "neon" colors.Ĭolor matching sucks, and trying to do it long distance is fraught with the danger of misunderstanding. It probably will not be a perfect match, but it will be a very close match unless your customer picked some wild out-of-gamut color that requires a special pigment. If he can't, one of his competitors probably can, although I am sure they would prefer a paint chip to scan. The paint guy should be able to find cross-reference charts for RAL, Federal standard, and Pantone process colors. Your paint vendor can scan a paint chip and give you the closest possible match in their color code system. Process color is what you probably want.) (BTW, Pantone has several color specification systems. The Pantone process color chart would also work although it's intended for ink on paper, not paint on metal. A decent reproduction of the RAL or Federal standard paint color charts would work, although the colors are fairly limited. Seriously: send him/her to a hardware or big box store with a paint department. Your customer needs to pick a color based on a paint chip, preferably a real physical paint chip. I am not going to get into additive vs subtractive colors, nor CIE Lab color space, nor gamut limitations, nor color models, nor any of the other highly technical crap behind the standard "your monitor may not show these colors correctly" warning. There are a lot of reasons you cannot reliably go from RGB to paint code.
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