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Blackbody, Black Body Radiation

SmartNote: 14
Type: Term
ColorGeek factor: unrated
A black body is a theoretical object which absorbs all light which strikes it and emits different wavelengths of light depending on the temperature to which it is heated. The color temperatures of 5000 degrees K, 6500 degrees K, etc all refer to the ?color temperature? of a black body heated to that temperature. Kelvin degrees are similar to degrees Celsius but start 273 degrees lower at absolute zero (0 degrees Celsius - freezing - is 273 degrees Kelvin)

See Also

Term: White point

Stock

SmartNote: 140
Type: Term
ColorGeek factor: unrated
The paper stock on which you print can have a major effect on your output. Stock comes in many forms and can range from newsprint all the way to plastic film. How inks are act when applied to paper is a complex issue and worthy of some discussion. There are several points worth considering:

Spot Color inks are opaque and Process Color inks are transparent.
What does this mean? Well, when you use Spot colors (like Pantone colors) the ink that is applied to the page on the press does not let light through to the paper and so is affected a lot less by the color of the paper. But, when using 3 or 4-color process inks, the ink is transparent (presumably so each ink color is able to modify the light) so the light hitting the page passes through the ink, gets reflected off the page, and then passes through the ink again before it travels to your eyes. This means that the color of the paper stock plays a huge role in determining the final look of your output.
It also means that spot colors emulated on a 4-color proofing device are affected by the proofing stock much more than they will be on the final press output. Nasty!
What do I do about it? A well-made printer profile should take paper stock color into consideration but you should note that the Rendering Intent you select will or will not correct for the stock color? choose this carefully.

Ink Absorption and Dot Gain
If the stock you are using is absorbent and the inks are liquid (as opposed to wax or toner as in many proofing printers) then the ink will "wick" into the paper as it is applied. This makes the dots fuzzier and larger and is one of the contributors to Dot Gain. For example, if you print a 10% cyan square on the page and then take a reading of the square with a Densitometer, you may find that it is in fact a 15% cyan square. This means your printer or press has a 5% dot gain.
What do I do about it? Again, a printer profile should automatically take dot gain into consideration and compensate for it. This is yet another reason to profile for every paper stock you use, as each one will affect ink differently.

See Also

Term: Ink
Term: Dot Gain

Subtractive primaries

SmartNote: 141
Type: Term
ColorGeek factor: unrated
Cyan, Magenta, and Yellow are subtractive primary colors. That is, in an imaging system which creates colors by using inks or other pigments (printers, presses, some proofing systems), cyan, magenta and yellow can combine in equal quantities to produce black (actually muddy brown in most cases - that's one of the reasons black is usually used). All the colors the device is able to create (the device?s gamut) are produced by varying the amounts of each ink color.

Subtractive colors get their name because they are thought of as subtracting light out of an image. Cyan, for instance subtracts (absorbs) red light. If less red is required in a color, more cyan ink is added.

See Also

Term: CMYK Cyan, Magenta, Yellow, Black
Term: Additive Primary Colors
Term: RGB