||Using the Pantone Color Cue for Matching Paint Colors|
For a more general discussion of matching cabinet paint colors, see the color matching page on this web site.
The Pantone Matching System (PMS) has been around since the early 1960's and has been the industry standard for matching solid ink colors. The two main color printing methods are "solid" and "process, CMYK or four-color process". Solid (sometimes called "spot color") printing uses inks mixed to match each individual color. If a document has three colors, the press is set up with three colors of ink to match those colors. If the colors are referenced to particular PMS colors, the formulas for the inks are uniformly defined by Pantone so the colors will (in theory) always match. Process color printing uses mixtures of four colors (cyan, magenta, yellow and black) to make up a very wide range of colors. By printing these four colors in different intensities, thousands of different colors can be created. The art of color printing can fill (and has filled) many books, so we'll just cover some basic issues here.
Gamut, Color Space and the Human Eye
The human eye can discern many thousands if not millions of distinct colors, so color matching is no easy task. Inks and paints are combinations of dyes, pigments and other chemicals that filter the light that falls upon it to create colors. They do this by selectively absorbing or reflecting light depending on its wavelength within the visible light spectrum.
The Pantone color matching system currently contains 1114 distinct solid colors. Their process color guide covers over 3000 CMYK colors, although the CMYK process can create more than 3000 possible colors. However, the larger number of distinct process (CMYK) colors does not mean that a wider range of colors can be represented. In fact, the opposite is true. The 1114 distinct PMS colors generally cover a wider range of colors than the CMYK process can normally reproduce. This is evidenced by another useful product from Pantone: the Pantone Color Bridge (formerly called the Pantone Solid to Process Guide). The Pantone Color Bridge shows how each of the 1114 solid colors look when printed using standard CMYK process inks, and the difference between them are sometimes significant. Fancier inkjet printers can use six or more colors in order to print a wider range of colors, but this usually affects only the internal operation of the printing mechanism. The color information sent to the printer is the same, but with the additional ink colors available, the printer does a better job of reproducing them.
What about RGB?
Paints and inks use subtractive color models, since individual pigments selectively absorb different frequencies. If you mix two different pigments, they each absorb their own colors so the resulting color is the color of the light source minus all of the colors absorbed by the pigments. The red-green-blue (RGB) color model used in the television and computer displays is an additive color model. The display emits specific colors rather than absorbs them, so the result of multiple color transmissions is the sum of all of the color sources.
So for this discussion, the RGB color space doesn't help us very much. But since the gamut of RGB colors is at least as wide as all of the others so far, we can translate other colors into RGB and out again without losing much information. Note that doing the opposite (e.g. translating an arbitrary RGB color into a PMS solid color) may drastically change the resultant color. RGB colors are usually represented by the values of 0 to 255 for each of red, green and blue (or their hexadecimal equivalents of 00 to FF). While this is very convenient for computers, and is more than accurate enough for our color matching purposes, there are a number of even more accurate color space models, and for the most accurate use of the Pantone Color Cue, none of RGB, PMS or CMYK is the best.
The RGB color space was developed because it corresponds to the three colors that the human eye can detect, and it corresponds (not coincidentally) with the transmission colors of the vast majority of television and computer displays. RGB assumes a linear relationship of chroma and luminosity (50% red, 50% green and 50% blue should correspond to 50% gray), but human color perception is not linear in either of those relationships. So all color rendering systems include gamma correction factors in an attempt to translate the linear RGB color space to the non-linear color response of the human eye. This gamma correction is a necessary part of color rendering, but it is not part of the RGB specification. The Color Cue can display RGB values as sRGB, which incorporates an industry-standard gamma correction profile, or colors can be displayed as AdobeRGB, using Adobe's RGB gamma correction, which provides a wider color space than sRGB. The take-away from all this is that RGB is a reassuringly simple way of representing colors, but as is the case with the Pantone Color Matching system, the answer that you end up with may not necessarily be what you want.
The Pantone Color Cue is capable of displaying the measured color in a variety of color spaces, but as we will see later, the most accurate color measurements can only be displayed in two other color spaces: CIE L*a*b* and XYZ (tristimulus). Follow the links for a description of how these color spaces work, but suffice to say that they all simply render the measured color into three separate numbers. It's the mathematical representation of the particular color space that determines the significance of the numbers. So when we get to using the Color Cue in its most accurate mode, we will be switching to one of these alternate color spaces - not because we need so much color-measuring accuracy, but that's how we get the Color Cue to work in its higher resolution mode. More on that a little later.
Pantone Color Cue Basic Operations
The Pantone Color Cue is an amazing device, and with some menu setting adjustments, it can be even more useful for paint color matching. Here's how the Color Cue works "out of the box". Turn it on, put it on top of the color you want to measure, press the button and the LCD tells you the closest Pantone PMS color. Incredible. If pinball machine cabinets used Pantone inks, the problem of color matching would be completely solved, because this device would identify the original color that was used, which you could then simply re-apply. However, there are two problems:
Getting More Accurate Color Information from the Color Cue
When you press the measurement button on the Color Cue, the results are displayed instantly on the LCD. When you press the "next" button, the color is displayed in a number of different formats, such as CMYK, sRGB, Adobe-compatible RGB, and more. We can turn off some of the less useful formats and there are also some measurement display formats that default to "off" that we will want to turn on. Here are the recommended changes:
The Color Cue will still display the closest PMS color, but now when you press the "next" button you will be able to see the raw color measurements coming from the color sensor. This is evident by taking multiple measurements at slightly different spots. Typically, the same PMS color will come up, but if you look at the other data display types (other than sRGB255), you will see that they change slightly each time.
You have also turned on the Display dE option, which shows up as a number after "dE=" in the LCD. This number indicates how far away the measured color is from the PMS color number that is displayed. Roughly, a dE number less than 1 is undetectably different, and numbers greater than 1 indicate approximately the number of discernable hues in between the measured color and the reported PMS color. It's surprising sometimes how far off the PMS color is from the measured paint color.
If you get a dE number of 1.0 or less, the PMS color is accurate for any color-matching tasks. In those cases, you can take either the PMS color number or the sRGB255 values as the color that you want to match up with paint. If the dE number is greater than 1.0, you should use the more accurate iLab or iXYZ values instead. Don't use the sRGB255 values in this case because the sRGB255 value is rounded to the nearest PMS color, not the measured color (which you know are significantly different because if the dE is greater than 1.0). The iLab data display typically looks like this:
This corresponds to L = 95.4, a = -0.3 and b = -1.3. For iXYZ, the data display may look like this:
This corresponds to X = 82.90, Y = 88.19 and Z = 96.67. There apparently wasn't room in the LCD for the decimal points, so you need to add them yourself.
So once you've transcribed the most accurate color codes, the next step is to match them to a paint color. Thanks to some nifty web sites out there, you can easily convert the less common XYZ and L*a*b* color formats to RGB, and from RGB we can actually go for a paint color match. If you're interested in learning more about color space conversion, here's the Wikipedia entry for the CIE Lab color space.
"Matching" Cabinet Colors with Modern Paints
We are often asked for paint color codes and for sources to obtain the right type and color paint for re-painting pinball machine cabinets. These are very difficult questions to answer on an individual basis and they are impossible to give answers that would apply to everyone. Here are some of the issues that can vary from case to case:
Some paint suppliers may be able to work from RGB or PMS color descriptions, but most would probably be baffled, confused, or they would just screw it up. So from here on, all we can offer are a number of suggestions. Don't miss the last one - it's an incredible on-line resource!
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