The measurement of the difference between a target brightness and the brightness achieved. Gamma difference is created by some electrical devices when displaying or recording image information. Examples of this are CRT phosphors, LCD cells, and CCDs in digital cameras. The electrical devices record/display brightness based on electrical current, but the amount of current does not usually effect brightness in a linear fashion. An increase in voltage at a low brightness level may not produce the same amount of change as an increase of the same amount of voltage at a high brightness setting.

Whether the device produces high gamma, low gamma, or no gamma is specific to each device. Different devices handle gamma compensation differently. This is why some digital cameras have washed out looking pictures, and some are too dark.

Most image editing programs have a gamma adjuster which will correct the gamma. Because all monitors have different "correct" gamma levels, most monitors have special drivers that tell the computer how to compensate for it. Video cards also have different gamma settings, and most computer games have ways to adjust the gamma.

Low Gamma	Correct Gamma	High Gamma

Pixels on screen are arranged in square formations. This is optimum because they can create precise vertical and horizontal lines. When diagonal lines or curves are used, a stair step effect is created. This is because the sloped line or curve has to be made out of tiny square pixels. As resolution increases, the amount of stair stepping decreases, because pixel size decreases, allowing the line or curve to be made with finer precision.

Without AA	With AA

Newer video cards can do anti-aliasing in game, allowing for a smoother and less jagged pixel. They this by either super sampling or using jitter effect.

Super sampling is when the image is rendered as a larger size and scaling down. This will resample the pixels to create a softer, more blended image.
Jitter effect is currently used by 3Dfx video cards. This process is faster performing, and higher in quality. What is done is that each frame is blended with the same frame contents, only offset by fractions of a pixel. This blends each pixel, and this jittering can be up to 8 times without severely limiting performance.

Banding & Dithering | Gamma & Anti-Aliasing