Overscan and underscan




Most television display manufacturers "overscan" the pictures on their displays (CRTs and PDPs, LCDs etc.), so that the effective on-screen picture may be reduced from 720 × 576 (480) to 680 × 550 (450), for example. The size of the invisible area somewhat depends on the display device. HD televisions do this as well, to a similar extent.

Computer displays including projectors generally do not overscan although many models (particularly CRT displays) allow it. CRT displays tend to be underscanned in stock configurations, to compensate for the increasing distortions at the corners.

Comments

Post a Comment

Popular posts from this blog

Current standards

Image
Televisions edit Televisions are of the following resolutions: Standard-definition television (SDTV): 480i (NTSC-compatible digital standard employing two interlaced fields of 243 lines each) 576i (PAL-compatible digital standard employing two interlaced fields of 288 lines each) Enhanced-definition television (EDTV): 480p ( 720 × 480 progressive scan) 576p ( 720 × 576 progressive scan) High-definition television (HDTV): 720p ( 1280 × 720 progressive scan) 1080i ( 1920 × 1080 split into two interlaced fields of 540 lines) 1080p ( 1920 × 1080 progressive scan) Ultra-high-definition television (UHDTV): 4K UHD ( 3840 × 2160 progressive scan) 8K UHD ( 7680 × 4320 progressive scan) Computer monitors edit Computer monitors have traditionally possessed higher resolutions than most televisions. 2000s edit In 2002, 1024 × 768 eXtended Graphics Array was the most common display resolution. Many web sites and multimedia products were re-designed from the previous 800 × 600 format...
Read more

Display resolution

Image
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 co...
Read more

Considerations

Image
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. 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 ...
Read more