A term used to measure relative monitor brightness. Standard gamma settings are 1.8 for Macintosh and 2.2 for Windows.


The range of unique colors that can be created for a given color model such as RGB or CMYK. Also referred to as color space.

GIF file

An efficient, compact file, perfect for use on the Web. GIF files create a color lookup table (CLUT) for each image; each color (up to 256 colors) in the image is categorized and stored in the CLUT. Because of this table (as well as algorithms that track repeating pixels), GIF files compress very well.


A fill that gradually blends two or more colors together.


The method for creating a continuous-tone monochrome image using a tonal palette consisting of 256 shades of gray.


An underlying matrix of lines that can be used for general alignment of all items on the page.


A user-defined alignment line that is drawn from the rulers. Guides can also be used in ImageReady to slice an image for use on the Web.