Video Production Resolution

Resolution

Analog television systems use interlace scanning with two sequential scans (50 or 60 fields per second), one with the odd numbered lines, the other with the even numbered lines to give a complete picture (25 or 30 frames per second). This is done to save transmission bandwidth but a consequence is that in picture tube (CRT) displays, the full vertical resolution cannot be realized. For example, the maximum detail in the vertical direction would be for adjacent lines to be alternately black then white. This is not a problem in a progressive display but an interlace display will have an unacceptable flicker or twitter at the slower frame rate. This is why interlace is unacceptable for fine detail such as computer word processing or spreadsheets. For television it means that if the picture is intended for interlace displays the picture must be vertically filtered to remove this objectionable flicker with a reduction of vertical resolution. According to the Kell factor the reduction is to about 85%, so a 576 line PAL interlace display only has about 480 lines vertical resolution, and a 486 line NTSC interlace display has a resolution of approximately 410 lines vertical. Similarly, 1080i digital interlaced video would need to be filtered to about 910 lines for an interlaced display, although a fixed pixel display (such as LCD) eliminates the inaccuracies of scanning, and thus can achieve Kell factors as high as 95% or 1020 lines.

Fixed pixel array displays such as LCDs, plasmas, DLPs, LCoS, etc. need a "scaling" processor with frame memory, which, depending on the processing system, effectively converts an incoming interlaced picture into progressive. A similar process occurs in a PC and its display with interlaced video (e.g., from a TV tuner card). The downside is that interlace motion artifacts are almost impossible to remove resulting in horizontal "toothed" edges on moving objects.

Also in analog connected picture displays such as CRT TV sets, the horizontal scanlines are not divided into pixels, and therefore the horizontal resolution is related to the bandwidth of the luminance and chroma signals. For television, the analog bandwidth for luminance in standard definition can vary from 3 MHz (approximately 330 lines edge-to-edge; VHS) to 4.2 MHz (440 lines; live analog tv) up to 7 MHz (660 lines; DVD). In high definition the bandwidth is 37 MHz (720p/1080i) or 74 MHz (1080p/60).

Televisions are of the following resolutions:

SDTV: 480i (NTSC, 720×480 split into two 240-line fields)
SDTV: 576i (PAL, 720×576 split into two 288-line fields)
EDTV: 480p (NTSC, 720×480)
HDTV: 720p (1280×720)
HDTV: 1080i (1280×1080, 1440×1080, or 1920×1080 split into two 540-line fields)
HDTV: 1080p (1920*1080 progressive scan)


Computers have higher resolutions:

Currently, 1024x768 is regarded as an acceptable default. As of July, 2002, 1024×768 Extended Graphics Array was the most common display resolution.[1][2] Many web sites and multimedia products were re-designed from the previous 800×600 format to the higher 1024×768-optimized layout. The validity of this method of gathering statistics is diminishing, however, as LCD monitors have only one native display resolution - the highest available on that particular monitor. When users select a lower resolution, the lower resolution is reported to the statistics gathering website. Nevertheless, the actual number of pixels in front of the user has not changed. Instead, interpolation in the monitor causes the picture to become fuzzy as it attempts to display an image of the wrong resolution by scaling it.

The availability of inexpensive LCD monitors has made the 5:4 aspect ratio resolution of 1280×1024 more popular for desktop usage. Many computer users including CAD users, graphic artists and video game players run their computers at 1600×1200 resolution (UXGA, Ultra-eXtended) or higher if they have the necessary equipment. Other recently available resolutions include oversize aspects like 1400×1050 SXGA+ and wide aspects like 1280×720 WXGA, 1680×1050 WSXGA+, and 1920×1200 WUXGA. The most common computer display resolutions are as follows[3]: A new HD resolution has been released mainly in 30" LCD monitors. The new 2560x1600 is the current max resolution WQXGA.

When a computer display resolution is set higher than the physical screen resolution, some video drivers make the virtual screen scrollable over the physical screen. Most LCD manufacturers do make note of the panel's native resolution as working in a non-native resolution on LCDs will result in a poorer image, due to dropping of pixels to make the image fit (when using DVI) or insufficient sampling of the analog signal (when using VGA connector). Few CRT manufacturers will quote the true native resolution since CRTs are analog in nature and can vary their display from as low as 320×200 (emulation of older computers or game consoles) to as high as the internal board will allow, or the image becomes too detailed for the vacuum tube to recreate (i.e. analog blur). Thus CRTs provide a variability in resolution that LCDs can not provide (LCDs have fixed resolution).

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. In computer displays, overscan and underscan can be altered by adjusting vertical blanking interval. CRT displays tend to be underscanned in stock configurations, to compensate the increasing distortions at the corners. On LCD and other flat panel displays, VBI can be lowered to support higher resolutions and refresh rate for the same bandwidth.