Display resolution

The display resolution or display modes of a digital television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT) displays, flat-panel displays (including liquid-crystal displays) and projection displays using fixed picture-element (pixel) arrays.In this image of a Commodore 64 startup screen, the overscan region (the lighter-coloured border) would have been barely visible when shown on a normal television.A 640 × 200 display as produced by a monitor (left) and television16-color (top) and 256-color (bottom) progressive images from a 1980s VGA card. Dithering is used to overcome color limitations. The display resolution or display modes of a digital television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT) displays, flat-panel displays (including liquid-crystal displays) and projection displays using fixed picture-element (pixel) arrays. It is usually quoted as width × height, with the units in pixels: for example, '1024 × 768' means the width is 1024 pixels and the height is 768 pixels. This example would normally be spoken as 'ten twenty-four by seven sixty-eight' or 'ten twenty-four by seven six eight'. One use of the term 'display resolution' applies to fixed-pixel-array displays such as plasma display panels (PDP), liquid-crystal displays (LCD), Digital Light Processing (DLP) projectors, OLED displays, and similar technologies, and is simply the physical number of columns and rows of pixels creating the display (e.g. 1920 × 1080). A consequence of having a fixed-grid display is that, for multi-format video inputs, all displays need a 'scaling engine' (a digital video processor that includes a memory array) to match the incoming picture format to the display. For device displays such as phones, tablets, monitors and televisions, the use of the word resolution as defined above is a misnomer, though common. The term 'display resolution' is usually used to mean pixel dimensions, the number of pixels in each dimension (e.g. 1920 × 1080), which does not tell anything about the pixel density of the display on which the image is actually formed: resolution properly refers to the pixel density, the number of pixels per unit distance or area, not total number of pixels. In digital measurement, the display resolution would be given in pixels per inch (PPI). In analog measurement, if the screen is 10 inches high, then the horizontal resolution is measured across a square 10 inches wide. For television standards, this is typically stated as 'lines horizontal resolution, per picture height'; for example, analog NTSC TVs can typically display about 340 lines of 'per picture height' horizontal resolution from over-the-air sources, which is equivalent to about 440 total lines of actual picture information from left edge to right edge. Some commentators also use display resolution to indicate a range of input formats that the display's input electronics will accept and often include formats greater than the screen's native grid size even though they have to be down-scaled to match the screen's parameters (e.g. accepting a 1920 × 1080 input on a display with a native 1366 × 768 pixel array). In the case of television inputs, many manufacturers will take the input and zoom it out to 'overscan' the display by as much as 5% so input resolution is not necessarily display resolution. Graphics wise, the input rate of resolution only changes frame rate by a little bit (e.g. 1080p - 720p = 5f). The eye's perception of display resolution can be affected by a number of factors – see image resolution and optical resolution. One factor is the display screen's rectangular shape, which is expressed as the ratio of the physical picture width to the physical picture height. This is known as the aspect ratio. A screen's physical aspect ratio and the individual pixels' aspect ratio may not necessarily be the same. An array of 1280 × 720 on a 16:9 display has square pixels, but an array of 1024 × 768 on a 16:9 display has oblong pixels. An example of pixel shape affecting 'resolution' or perceived sharpness: displaying more information in a smaller area using a higher resolution makes the image much clearer or 'sharper'. However, most recent screen technologies are fixed at a certain resolution; making the resolution lower on these kinds of screens will greatly decrease sharpness, as an interpolation process is used to 'fix' the non-native resolution input into the display's native resolution output. While some CRT-based displays may use digital video processing that involves image scaling using memory arrays, ultimately 'display resolution' in CRT-type displays is affected by different parameters such as spot size and focus, astigmatic effects in the display corners, the color phosphor pitch shadow mask (such as Trinitron) in color displays, and the video bandwidth.