Dot pitch

Dot pitch (sometimes called line pitch or phosphor pitch) is a specification for a computer display that describes the distance between phosphor dots (sub-pixels) or LCD cells of the same color on the inside of a display screen. Thus, dot pitch is a measure of the size of a triad plus the distance between the triads.

Measured in millimetres, a smaller number generally means a sharper image, and vice versa, as there are more dots in an area of any given size. Note, however, that a monitor with a smaller dot pitch usually has a better-quality image, but by no means always, due to a number of factors, including:

measurement method not documented, complicated by general ignorance of the existence of multiple methods
differing pixel geometries
differing screen resolutions when attempting to judge picture quality
tightness of electron beam focus and aim

Traditionally, dot pitch was always measured on the diagonal, as this gives the most accurate representation of the monitor. Starting about the mid-1990s, however, some companies introduced a horizontal dot pitch as a marketing ploy. By measuring only the horizontal component of the dot pitch and ignoring the vertical component, even a cheap, low-quality monitor could be awarded a small-seeming dot pitch.

The exact difference between horizontal and diagonal dot pitch varies with the design of the monitor (see Pixel geometry), but a typical entry-level 0.28 mm (diagonal) monitor has a horizontal pitch of 0.24 or 0.25 mm, a good quality 0.26 mm (diagonal) unit has a horizontal pitch of 0.22 mm.

Some modern manufacturers quote dot pitch measurements made on the horizontal, others on the diagonal, and many use both. In general, low-end manufacturers tend to quote a horizontal measurement, while quality manufacturers tend to use the diagonal method, but there are many exceptions.

The above dot pitch measurement do not apply to aperture grille displays. Such monitors use continuous vertical phosphors band on the screen, so the vertical distance between scan lines are limited only by video input signal's vertical resolution and the thickness of electron beam, so there is no vertical 'dot pitch' on such devices. Aperture grille only has horizontal 'dot pitch', or otherwise known as 'stripe pitch'.

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