A Guide to Choosing the Right 19" LCD Monitor - 7 Models Reviewedby Kristopher Kubicki on November 30, 2004 12:04 AM EST
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How to Pick a Good LCD (continued)Color Depth: Almost all LCDs today are 6-bit or 8-bit LCDs. This means that each subpixel - Red, Green, and Blue - can display one of 2 to the n shades where n represents the number of pixels. A typical 8-bit LCD can produce 256 shades per pixel, or 16.7M color combinations. A 6-bit LCD panel can display 64 shades per subpixel, and since there are three subpixels per pixel, the monitor can display 262,000 color combinations per pixel. This is generally OK for gaming, but certainly not acceptable for any graphics development. Personally, I enjoy seeing the other 98% of the 24-bit color spectrum.
Brightness: Brightness is fortunately an easy specification to remember. More is better, particularly on LCDs with higher resolution. Even though your LCD might have six bulbs behind the substrate, a very small fraction of that light actually filters through the liquid crystal. Although, the measurement of "candela per meter squared" or "cd/m2" or "nits" all refer to the amount of light that actually passes through the front of the monitor at a 90 degree angle.
Viewing Angle: Viewing angle generally has a lot to do with the display mode of an LCD. You may wish to check out our LCD FAQ from a year ago that went through a lot of the basics of LCD design, particularly the pages on how LCD substrates work. Differing display modes utilize differing methods for twisting the LCD crystals - TN, PVA and SIPS are just a few. When LCDs were new, there were large issues with getting light to pass through the substrate at more angles than just 90 degrees head on, and for a short period of time, it was important that LCDs have some viewing angle. However, almost all LCDs today (and for the last 3 years or so) have viewing angles that are wide enough for anyone to look at the LCD from any (sane) angle. Unless you spend a lot of time looking at your monitor from 3 feet away, 60 degrees off center and at a 45 degree incline, don't worry about viewing angle so much when buying an LCD. We generally only mention viewing angle in our reviews if something seems amiss.
Contrast Ratios: Contrast measurements were originally supposed to quantify the difference between the lightest light and the darkest dark on the LCD. For example, if a black portion of the screen has a brightness of 0.5 cd/m2, and a white portion has a brightness of 250 cd/m2, then the monitor would have a contrast level of 500:1. Almost immediately, this measurement has been abused; manufacturers can take these measurements on angles to assure darker darks and brighter brights. Furthermore, other manufacturers take these measurements in different light settings and with different test pattern (some take measurements with the screen completely dark, while others take measurements with the screen in a checkerboard pattern). Unfortunately, relying on manufacturer Contrast Ratios too heavily during a purchase will probably lead you astray. To correct that, we will run a standardized test in our lab that tests contrast ratios of all of our LCDs in controlled situations.
So far, we covered only the introductory basics in shopping for an LCD. Footprint, features and rotation capabilities are all important as well, but don't be awed by monitors with features that you will never use. Paying $50 extra for MagicBright or a TV tuner only makes sense if you're going to use it.