Three Color Models
Methods for Describing Color
The RGB Model -
The RGB model is the one used to emit light on computer monitors. It has three primary colors of Red, Green, and Blue. All colors you see on your monitor screen are achieved by combining these colors in varying proportions. The strength of each of these colors is described by numerical values ranging from 0 to 255. See the example below.
........................RED.......GREEN........BLUE.........Color Produced
Strength.............0.................0...................0............Pure
Black
Strength.........255.................0...................0............Pure Red
Strength.............0.............255...................0............Pure Green
Strength.............0.................0...............255............Pure Blue
Strength.........255.............255...............255............Pure White
Red, green, and blue are referred to a additive because they combine to yield white. The absence of any emitted color is black, this is the color of a blank screen or your monitors screen when there is no power.
The CMYK Model -
The CMYK model is one of the Subtractive Color Models which is based on light being absorbed and reflected by paint or ink. This model is used for printing. The primary colors are Cyan, Magenta, and Yellow. When all three are combined they produce black. Because of impurities in ink it is difficult to produce a true black. This is why they have added a fourth color blacK; hence the K in CMYK. This is the reason some ink jet printers have a black cartridge in addition to the color one. You can now begin to see why it is difficult to obtain an exact match of the colors viewed on the monitor to the colors printed on paper. Also different papers absorb various inks at different rates. Also monitors, like TV screens, have adjustments which can vary the appearance of shades and colors. Another contributing factor is that different people see colors differently.
The HSL Model -
This model defines color using Hue, Saturation, and Lightness. These are also measured on a scale of 0 to 255.
Hue
distinguishes the various colors such as Red, Orange, Yellow, Green, Cyan, Blue, Magenta, and finally back to Red. These are the colors you would experience as you move through the color spectrum. Red has a value of either 0 or 255. Yellow is a value of 45, green is at 85, and Cyan is the opposite or inverse of red and it is at a value of 128. Blue is 170, Magenta is 212. Notice that Blue is opposite of Yellow and Magenta is the opposite of Green on this color scale or wheel.Saturation
is the strength of a hue, or the amount of gray it contains. Vivid colors (very little gray) has a high saturation level or number. As the saturation decreases the amount of gray increases.Lightness
is the amount of perceived intensity of light. A value of 0 is total darkness or black. A value of 255 is total lightness or white. On this scale a value of 127 (50% lightness) is considered a pure hue.
In Paint Shop Pro the removal of hue from an image is referred to as Gray Scale. A gray scale image contains 256 levels of gray or lightness. This is similar to the old black and white TVs.
Color Channels
are planes of color which images are organized in. An RGB image has three channels while a CMYK image has four. Graphics programs usually contain instructions for the computer to allow conversion from one type to another. All printer software must have this capability if it prints graphics.