With the growing popularity of LCD (Liquid Crystal Display) displays for both computer and home entertainment use and the advent of larger LCD displays on notebooks, it is a good idea to understand the basics of screen resolutions. There are a lot of terms in general usage, such as native resolution, aspect ratio and so on, that are sometimes confusing. This article discusses various screen resolution specifications and how they affect performance.
Screen resolution is measured in pixels (from the term picture element), the smallest units of information shown on a display. By convention, resolution is given in horizontal pixels by the number of vertical pixels. For example, an 800 x 600 resolution (also known as SVGA, or super video graphics array) is 800 pixels wide by 600 pixels tall, for a total of 480,000 pixels. The total number of pixels that appear on-screen can also be measured in millions of pixels or mega pixels, abbreviated mp. So, a display with a resolution of 800 x 600 is a 0.48 mp display. The higher the total numbers of pixels, the higher the resolution.
The ratio of horizontal pixels to vertical pixels is the aspect ratio of a display. A resolution of 800 x 600 has an aspect ratio of 800/600 or 1.33. Aspect ratio is more commonly expressed using the smallest possible whole numbers separated by a colon. For example, the aspect ratio for 800 x 600 would be expressed as 4:3.
The traditional proportion in width to height for a TV and computer monitor is 4:3, but some new screens, especially on larger TV/PC displays and laptop screens, have a wider format, 16:9 or 16:10, that has been designed for viewing movies or HDTV in wide format.
A 17” wide-format panel has about the same vertical dimension and vertical pixel count as a normal 15” panel, so you get about 120 percent more viewing area with the wider format. A 17” standard panel, however, has 130 percent of the viewing area of a 15” standard screen. This is due to the way that screen sizes are measured it is the diagonal distance from one corner to the opposite corner. So a 17” wide screen is actually smaller in total screen area than a 17” standard.
If different resolutions with different aspect ratios are viewed with the same computer monitor, each will appear taller, shorter, wider or narrower than another resolution. This is because a different number of horizontal and vertical pixels are being squashed or stretched onto the same physical area.
The physical structure of some types of displays, including LCDs and plasma panels, defines how many pixels can be displayed at once. The highest resolution supported by a display is often called its native resolution. At this resolution, each pixel is individually rendered and clearly defined and this results in a sharper, clearer screen image.
Other types of displays, such as CRTs, create pixels independently of the physical structure of their screens and do not have a native resolution. As a result, a CRT's image quality is generally the same across a range of resolutions.
At lower resolutions, LCD display scaling may occur and, as a result, the screen image may appear blurry because the selected display resolution is resized (and filtered) to fit on the screen. It can also distort the image by having to compress the pixels resulting in colour blending and a loss of sharpness.
Screen geometry describes how accurately lines and shapes are represented on the display. LCDs almost always have perfect geometry because the display information is mapped to specific physical pixels on the display. This was one of the problems with CRTs: larger screens and flat-faced models had particular difficulty controlling electron beams with precision. As a result, vertical lines could have been noticeably curved at the edges of the display, and circles appeared oval or egg-shaped.
Here is an overview of the most common 4:3 aspect ratio screen resolutions:
VGA
Video Graphics Array. 640 x 480 pixels or .31 mp. 4:3 aspect ratio. VGA was once considered the base resolution and was supported by most graphics hardware and monitors. Typically used with 14” and 15” CRT screens.
SVGA
Super VGA. 800 x 600 pixels or .48 mp. 4:3 aspect ratio. First defined by the VESA (Video Electronics Association) in 1989. Because most current graphics hardware and monitors support SVGA, systems often use it as the default resolution. SVGA is a common resolution for 10.4" and 12" screens in notebook PCs.
XGA
eXtended Graphics Array. 1024 x 768 pixels or .79 mp. 4:3 aspect ratio.
XGA+
XGA plus. 1152 x 864 pixels, or 1.00 mp; 4:3 aspect ratio. Extension of the XGA standard.
QVGA
Quad VGA. 1280 x 960 or 1.23 mp; 4:3 aspect ratio. Four times as many pixels as VGA.
SXGA
Super XGA. 1280 x 1024 pixels, or 1.31 mp; 5:4 aspect ratio. Next step up from XGA. Not exactly a 4:3 aspect ratio, but close. Typically used with 17” and 19” screens.
SXGA+
Super XGA plus. 1400 x 1050 pixels, or 1.47 mp; 4:3 aspect ratio. Extension to SXGA+.
UXGA
Ultra XGA. 1600 x 1200 pixels, or 1.92 mp; 4:3 aspect ratio. This resolution has four times the resolution of SVGA. Typically used with 21” or larger screens
QXGA
Quad XGA. 2048 x 1536 pixels or 3.15 mp; 4:3 aspect ratio. Four times as many pixels as XGA. Can be configured as a single signal in four separate XGA displays.
QSXGA
Quad XGA. 2560 x 2048 pixels or 5.24 mp; 5:4 aspect ratio. Not exactly a 4:3 aspect ratio, but close. Four times as many pixels as SXGA. Can be configured as a single signal in four separate SXGA displays.
QUXGA
Quad UXGA. 3200 x 2400 pixels, or 7.68 mp; 4:3 aspect ratio. This resolution has four times the resolution of UXGA.
These are the leading wide-format resolutions:
WXGA
Wide XGA. 1280 x 800 pixels, or 1.02 mp; 16:10 aspect ratio. A wider version of the XGA (1024 x 768 pixels).
WXGA+
Wide XGA plus. 1440 x 900 pixels, or 1.30 mp; 16:10 aspect ratio. An extension of the WXGA resolution. Typically used with 19” screens.
WSXGA
Wide SXGA. 1600 x 1024 pixels, or 1.64 mp; 25:16 aspect ratio. A wider version of the SXGA (1280 x 1024 pixels) resolution.
WSXGA+
Wide SXGA plus. 1680 x 1050 pixels, or 1.64 mp; 16:10 aspect ratio. An extension of the WSXGA resolution. Typically used with 20” screens.
WUXGA
Wide UXGA. 1920 x 1200 pixels, or 2.30 mp; 16:10 aspect ratio. A wider version of the UXGA (1600 x 1200 pixels) resolution. Typically used with 24” screens.
WQXGA
Wide QXGA. 2560 x 1600 pixels, or 4.10 mp; 16:10 aspect ratio. A wider version of the UXGA (1600 x 1200 pixels) resolution. Typically used with 30” screens.
WQUXGA
Wide QUXGA. 3840 x 2400 pixels, or 9.22 mp; 16:10 aspect ratio. A wider version of the QUXGA (3200 x 2400 pixels) resolution.
As you can see, there is a certain symmetry in the naming conventions.
Q:
What is the pixel-response rate?
A:
This refers to how quickly a pixel can change colours, measured in milliseconds (ms). The fewer the milliseconds, the faster the pixels can change, reducing the ghosting or streaking effect you might see in a moving or changing image.
Q:
Is clarity the only advantage of a higher resolution?
A:
Higher resolutions can also display more information on the screen. On a Windows desk top, you can see 2-3 times as many icons in a 1280 x 1024 (SXGA) resolution as in a 800 x 600 (SVGA).
Q:
Can you have too high a resolution?
A:
If you set the resolution too high on a relatively small-sized display, the icons, fonts and images will become too small to be legible. Resolution and screen size must be somewhat matched.
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