Display contrast

Contrast, in physics and digital imaging, is a quantifiable property used to describe the difference in appearance between elements within a visual field.

It is closely linked with the perceived brightness of objects and is typically defined by specific formulas that involve the luminances of the stimuli.

Understanding contrast is crucial in fields such as imaging and display technologies, where it significantly affects the quality of visual content rendering.

The contrast of electronic visual displays is influenced by the type of signal driving mechanism used, which can be either analog or digital.

This mechanism directly influences how well the display renders images under varying conditions.

Additionally, the contrast is affected by ambient illumination and the viewer's direction of observation, which can alter perceived brightness and color accuracy.

A modification of Weber by Hwaung/Peli adds a glare offset to the denominator to more accurately model computer displays.

This more accurately models the loss of contrast that occurs on darker display luminance due to ambient light conditions.

Two parts of a visual field can be of equal luminance, but their color (chromaticity) is different.

Such a color contrast can be described by a distance in a suitable chromaticity system (e.g. CIE 1976 UCS, CIELAB, CIELUV).

[citation needed] Any two test patterns that are not completely identical can be used to evaluate a contrast between them.

[citation needed] When the image content is changing rapidly, e.g. during the display of video or movie content, the optical state of the display may not reach the intended stable steady state because of slow response and thus the apparent contrast is reduced if compared to the static contrast.

There is quite some digital signal processing required for implementation of the dynamic contrast control technique in a way that is pleasing to the human visual system (e.g. no flicker effects must be induced).

[6] High-dynamic-range (HDR) LCDs are using that technique in order to realize (static) contrast values in the range of CR > 100.000.

This is the reason why most contrast ratios used for advertising purposes are measured under dark-room conditions (illuminance EDR ≤ 1 lx).

100 lx) or in an office situation (illuminance 300 lx minimum), ambient light is reflected from the display surface, adding to the luminance of the dark state and thus reducing the contrast considerably.

[citation needed] A quite novel TV-screen realized with OLED technology is specified with a dark-room contrast ratio CR = 1.000.000 (one million).

[citation needed] If the reflective properties of the projection screen (usually depending on direction) are included in the measurement, the luminance reflected from the centers of the rectangles has to be measured for a (set of) specific directions of observation.