Holiday 2008 Display Guide

The Eyes Have It

Choosing an appropriate display can often get very confusing, particularly if you don't know the terminology. We've covered this in our display reviews, so if you're not sure what the various specifications mean you can start there. One area that we didn't cover in that glossary is panel technologies, but once again we've discussed that elsewhere. For those that don't like to follow links, here's a recap.

Many LCD specifications are prone to inflation by the manufacturers or have become largely meaningless. Take contrast ratio for example. That's the white level divided by the black level, and if you could actually get pure black on any LCD contrast ratio would be "infinity". In practice, anything over 500:1 is sufficient, and 1000:1 is about the best you can see before the manufacturers start playing tricks. What sort of tricks? How about dynamic contrast ratio, where the backlight intensity changes according to the content currently being shown on the display. Now you can take the maximum white level at maximum brightness and divide it by the minimum black level at minimum brightness, which results in substantially higher contrast ratios. Unfortunately, in practice the varying intensity of the backlight can be distracting to say the least, and color accuracy greatly suffers because of the constantly shifting brightness levels. Our advice: ignore dynamic contrast ratios, and if your display supports the feature we recommend disabling it.

Pixel response times are another area that has been inflated -- or deflated in this case. We have looked at various LCDs boasting anywhere from a 2ms to 16ms response time; honestly, we would be hard-pressed to tell the difference between most of them. All of the comparison images we've captured show similar best/worst case scenarios for pixel response latency, with one or two afterimages present. A bigger problem these days is processing lag (aka "input lag"), which is the delay between the time a signal is sent to your LCD and the time the internal circuitry finishes processing it and actually shows it on the LCD panel. We have measured lag as high as 50ms, which makes gaming very frustrating and is even noticeable/irritating during general Windows usage.

The one item that manufacturers don't usually make a big deal about happens to be the aspect of any display that seems to matter most: the actual panel technology. There are three general categories of panel technology: TN (twisted nematic), MVA/PVA (multi-domain vertical alignment/patterned vertical alignment), and IPS (in-plane switching). Opinions about which technology is actually best differ somewhat, but there's no denying the fact that TN is substantially cheaper to produce whereas PVA and IPS are more expensive. These days, the vast majority of LCDs are once again using TN panels, largely because of the pricing advantage. If you want a higher quality panel using MVA, PVA, or IPS you will need to be prepared to pay anywhere from 50% to 300% more -- depending on overall quality and the target market. Here's a quick overview of the panel technologies.

Viewing angles on TN are substantially worse, particularly vertical viewing angles, and all TN panels are natively 6-bit panels that use dithering to approximate 8-bit color. Most people won't notice the difference in color accuracy, but imaging professionals would definitely prefer something better. The advantage of TN panels is that -- at least on the ones we've tested -- input lag is not a problem. Response times are usually lower on paper, but again it's difficult to actually see the difference between a 2ms panel and a 6ms panel, especially when the display refreshes every 17ms.

PVA and IPS are basically the exact opposite of TN: great viewing angles, very good color reproduction, and true 8-bit colors. However, pixel response times are a little lower (it's not something that has ever bothered us). The other big problem? At least on the S-PVA panels that we've tested, input lag has been a major concern, ranging from as low as 20ms up to nearly 50ms. Ouch! S-IPS panels don't seem to have a problem with input lag, at least on the models we've tested -- which all happen to be 30" LCDs. That said, Dell's 3008WFP is the exception, which seems to be caused more by the digital scaler than by the IPS panel.

A less common panel type is MVA, which in practice is similar to PVA but seems to perform better in regards to input lag. We've only tested one LCD that uses an MVA panel, the BenQ FP241VW (a review is forthcoming), and input lag appears to be equal to that of our reference LCD. Color quality and other aspects are also good, but pricing and availability is a concern, not to mention the fact that we're not super keen on the frame/stand for the FP241VW.

That was a really long-winded introduction to our display choices, but it's important to understand the above information before you start looking at the various options. Frequently, the choice will come down to getting something larger with a cheaper TN panel versus getting a smaller LCD with a PVA/IPS panel. Even among the same panel technology, however, there are wide variations in quality. Most LCD panels are manufactured by one of only a few companies, but similar to processors these panels are "binned" based on quality. The bottom line is that you often get what you pay for, so if you're wondering why LCD X seems to have the same specifications as LCD Y but costs significantly less, it's very likely that the panel doesn't meet the same quality standards. Color uniformity is one of the big differences between various LCD panels, with the best panels often ending up in displays that cost twice as much as LCDs that are otherwise equal in terms of specs. So now let's look at our various recommendations for the different price points.