LCD Technology Part 1: Specs & Numbers

Among PC geeks, LCD jargon is now pretty much common knowledge, but most lay-folks still do not know the distinction between “LCD” and “LED.” Here is a basic beginner’s guide on the fundamentals of LCD technology. Part one is an explanation of what the numbers that manufacturers publish actually mean:

1. Resolution, Aspect Ratio & Screen Size: Everyone understands the sizes of screens, but too many do not question the actual resolution of each LCD. The higher the resolution, the more pixels a display can produce. “Aspect ratio” is how many pixels an LCD has horizontally in relation to its vertical number of pixels. For example, 1280×800 (1,024,000 pixels) is 16:10 aspect ratio (the standard ratio for HDTV). Generally, the following screen sizes represent the industry average number of pixels per screen for laptops:

- 13″ to 15″ - 1280×800 (16:10) known as “WXGA,” 1366×768 (16:9)
- 15″ to 16″ - 1440×900 (16:10) known as “WSXGA,” 1680×1050 (16:10) known as “WSXGA+”
- 17″ - 1920×1200 (16:10) known as “WUXGA,” 1920×1080 (16:9) known as “1080p”

LCDs should be run only at “native resolution,” the highest pixel number that each display panel supports. When an LCD is displaying a ratio or a certain number of pixels that it is not natively supporting, the image will be stretched (in the case of incongruous ratios) and blown up, resulting in image quality worse than the LCD is capable of producing.

2. Contrast Ratio: This is probably the most misleading and perplexing area of LCD (and plasma) technology. In a nutshell, contrast is simply how much darker the blacks are in contrast to the whites, so a ratio of 2000:1 means that the darkest black is 2000 times darker in luminance than the brightest white. Manufacturers love to sell their wares by advertising the biggest contrast ratio numbers, but all claims should be taken with some skepticism. To learn more about contrast ratios and the difference between “static” and “dynamic” contrast, refer to an informative paper by Practical Home Theater Guide.

3. Response Time & Input Lag: for far more knowledge than you require, read an essay about response time and image lag by Home Theater Guide. All that the public really needs to know about response times is that for desktop LCDs, around 8ms pixel response time at 60Hz is standard, and that higher-end HDTVs, which boast 120 and even 240Hz ratings at 2-5ms, can sometimes show slightly smoother images in between frames of animation depending on the source (such as a very fast game running at over 60 frames per second). Laptop numbers, of course, will be lower. “Input lag” is separate to response time and measures the time delay before the input of a source (your computer’s video card or cable box) is shown on the LCD. Manufacturers do not publish input lag numbers, but most “gaming” LCDs purport to have very low input lag. For some hardcore gamers, an LCD with too much lag could be unacceptable for serious use, but for average consumers, this is not a massive issue.

4. Colors & Color Gamut: nearly all LCDs claim to support 16.7 million colors, but the truth is that most consumer grade LCDs display only 262,144 colors and use “dithering” to trick viewers into “seeing” 16.7 million colors. Color “gamut” is not the number of colors, but the intensity or range of a given color. The higher color gamut rating (100% NTSC or more), the deeper and more saturated the three main hues - red, green, and blue - appear. As a comparison, CRTs show about 70% of the NTSC color gamut spectrum.

5. Viewing Angles: the three different panel types of LCDs are the biggest determinants of viewing angles, but the quality of each specific panel and its backlighting also affect things. Part two of this guide contains more information about viewing angles, which are given as vertical/horizontal numbers in degrees: e.g. 178/178.

6. Brightness & Luminance: an LCD’s level of brightness is measured in “nits” or cd/m2 (candelas per square meter). 200 nits is average for laptop monitors, while desktops are about 250 to 400.