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The Ultimate Guide to Color, Part I

Pots of color WARNING: This is going to be a little science-y at the beginning, but just stick with me and we’ll get to the good stuff. In order to understand how color works, we need to know what color is. The colors we see are the visible representations of the different wavelengths of light. How these wavelengths interact with objects determines how we perceive those colors. When something looks blue, it’s because that object is absorbing all the colors except blue; the blue wavelength is reflected, and that’s the wavelength that enters our eyes. This is a bare-bones explanation, but it gives you an understanding of what color really is and how we see it. So colors are types of light. There are two main color models: additive and subtractive. Subtractive color is the color model used by the printing process. Black is produced by combining colors together, and white is produced by the absence of colors. We start with white (a blank page), and only produce color when it’s put down on the page. This is called subtractive because colors must be subtracted from black in order to achieve white. The other color model, additive, works in the opposite way. It is a light-based color model and is how we see color with our eyes. It is also how we reproduce colors on things like televisions and Eye with color iriscomputer screens. When you combine, or add, all the colors of light together, they form white light (this is why when you shine white light into a prism, it will produce a rainbow). Since colors are portions of light, when you have no colors, you have black (darkness). Summation: with light, white is all the colors combined, and black is the absence of any colors. Colors must be added to black to produce white. Oy. Still with me? Good, because now we’re going to talk about the meat and potatoes. I’m talking about RGB vs. CMYK: the grudge match of the century. RGB is an example of an additive color model (others include HSB and Lab, but we’re not going to go down that rabbit hole just yet); CMYK is an example of a subtractive color model (another is hexachrome). RGB stands for Red-Green-Blue, because these are the three colors used to produce all other colors in this color model. If you look really closely at a television screen or monitor, you’ll see it’s made up of tons of little squares divided into three columns: red, green, and blue. When the screen is off, you have black (the absence of these colors being lit up). CMYK stands for Cyan-Magenta-Yellow-Black, the four colors used to produce all other colors in this color model. If you look really closely at any kind of printed material (a magazine, for instance), you’ll see that everything on the page is made up of tiny dots of one or more of these colors. Now, each color model has limitations in the colors it can express. Refer to the diagram and you Color diagramcan see that, in general, RGB has a wider gamut, or scope, than CMYK. However, also note that CMYK can achieve more yellows, oranges, and magentas than RGB. It is because of this that colors may appear much more vibrant on-screen than when they are printed. Of course, images can be converted from RGB to CMYK and vice-versa (and there are hundreds of different methods and settings for doing so, but we’ll save that for another post), but because RGB has the generally larger gamut, converting a CMYK image to RGB will not usually change its appearance. So you can’t just fix a CMYK image by converting it to RGB and call it a day, you usually have to go back to the source RGB file, if one is available, to achieve that sweet color vibrancy. You might say to yourself, You know, I noticed that sometimes when I print a picture it looks a lot different on the page than it did on my screen. This is not your printer’s fault (typically), it’s that your printer uses CMYK and your computer screen uses RGB. So when you print an RGB image, it’s converted on-the-fly for CMYK printer output. The printer software does the best it can, but the results are not optimal. By contrast, when CMYK images are used on-screen (e.g., on a website), they tend to appear much duller than their RGB counterparts. Takeaway: RGB can produce muddy prints, CMYK can produce dull on-screen imagery. The important thing to tie this all together: RGB is an additive color model, which is used for expressing color on screens; CMYK is a subtractive color model, which is used for expressing color in print. Because of this, it is essential that the correct color space be used for any images used in either medium in order to achieve maximum color output. No one wants dingy images for their projects, personal and professional alike. Derek Bedrosian is Senior Visual Designer at wedü. When he’s not coming up with awesome blog material, he’s creating awesome visual material. Or playing video games. Or making paper toys.
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