| Vikki Olds March 15, 2004 
Have you ever wondered why when you print an image the colors are different than they appeared on your monitor? I sure have. In this article we'll cover some of the why's about color and the screen and color and the printer. There are generally three color models; RGB which we see on our monitors, HSL which is what human eyes really see and CMYK which is used for printing. Monitors show color through emitted light or RGB (Red,Green,Blue), we see color through reflected light (Hue, Saturation, Lightness) and the printer has it's own way with color, CMYK (Cyan, Magenta, Yellow and Black). RGB (Red, Green, Blue) The computer screen emits color as RGB. RGB color or (Red,Green,Blue) is determined by numerical values associated with each part. Values can range for each part from 0 - 255 with 0 being the darkest value and 255 being the lightest. For instance, if you set the RGB color value to 0,0,0 you would have black. If you set it to 255,255,255 you would have white and if you set all values the same anywhere in between 0 and 255 you would have varying shades of gray. 
HSL (Hue, Saturation, Lightness) We see color as HSL. Hue is the color reflected from an object and has values from 0 - 255. Saturation is the purity and vividness of the color. Saturation represents the amount of gray in a color. It also has values ranging from 0 - 255 with 0 being fully gray and 255 being fully saturated color. Lightness Lightness reflects the intensity of light ranging from 0 (black) to 255 (white). When a color has 50% lightness it is considered pure. Pure red is Hue-255, Saturation-255, Lightness-128. Pure blue is Hue-170, Saturation-255, Lightness-128. 
CMYK CMYK (Cyan, Magenta, Yellow, Black) is used for printing. When I say printing I don't mean to your desktop printer. CMYK separations are for sending out to a commercial printer unless of course you have that equipment yourself. Combining inks in CMYK is called a four color process. CYMK are color separations. Images have color channels and each color in CMYK is represented in a color channel. When you use a graphics program to separate the colors what you end up with are four separate gray images that represent each of the color channels. 
Color Depth Color depth refers to the number of colors each pixel holds. The deeper the color depth the more colors there are. Pixel information is stored in computer bits and can be from 1 - 24. A one bit pixel can display only black or white. A 24 bit pixel can display on of 16 million colors. Computer monitors are limited by their capabilities. If you try to view a 24 bit image on a monitor that will only display 16 bit color you will end up with some color distortion. Just because you create an image with a bit depth of 24 doesn't mean that the image will actually use all those colors. It just means that the image is capable of using all those colors. That's the very basics of understanding a little about the differences in how we, our computers and our printers see color. There is a lot more to learn about color but at least you have an idea of how color works visually and hopefully that will help you choose colors that are right for your application.
Copyright 2004, Vikki Olds, All Rights Reserved | 