There are two common methods of measuring contrast — Full On/Off and ANSI Contrast. Full On/Off is easy to manipulate, it produces misleading numbers, and is commonly used in the industry. The ANSI method is difficult to manipulate, produces very small but much more valid and informative numbers, and is rarely used in the industry other than by manufacturers in specialty niches. Let’s take a look at the difference between them.
A Full On/Off Contrast reading measures the ratio between the brightness of a solid white, 100 IRE test pattern (“full on”), and the brightness of a solid black, 0 IRE test pattern (“full off”). A contrast ratio of 10,000:1 indicates that the meter is reading the white as being ten thousand times brighter than the black.
The ANSI Contrast method does not use the 100 IRE white and 0 IRE black screens. Instead, it uses a single checkerboard pattern of 16 rectangles, eight white and eight black. The brightness values of all the white squares are measured and averaged, and the brightness of the black squares are measured and averaged. The ratio of the averaged white readings to the black readings is the ANSI contrast ratio.
By Evan Powell
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