Actual area of a sub-pixel that transmits light, expressed as a percentage; higher aperture ratio designs enable brighter displays or lower power

The ratio of the effective lens opening to its focal length (1/ F#)

In digital display devices, this is a measure indicating the percentage of the available area that is used for active pixels. Some displays have obvious inactive 'frames' around individual pixels, leading to the description 'screen-door' effect when viewing such a display from insufficient distance.

Part of the light valve which represents the actual usable area for modulation of light. Also called geometrical aperture.