Recently I was in the market for a new monitor -- see the dead CRT article. CRTs are still quite a bit cheaper than LCDs, and still have advantages, but the remaining advantages are for usages that I don't care about. Needless to say, an LCD monitor seemed the most attractive option.
The industry tends to focus on four attributes of LCD panels: brightness, contrast ratio, "response time," and viewing angle. All of these are important. All of these are subject to inflation by marketers changing measurement standards rather than actually improving the panel. All but brightness tend to expose the weaknesses of LCDs compared to CRTs.
Perhaps the most telling aspect of an LCD panel is the liquid crystal organization. This detail seems to be considered too technical, and is either ignored, or intentionally left out of the discussion on most review sites, save a select few. There are three major competing technologies here, complete with acronyms:
- TN, or Twisted Nematic, is the simplest, oldest, and cheapest organization. TN panels are widely produced by many manufacturers, but tend to be restricted to sizes 19" and smaller. Presently, TN panels dominate the laptop display and low-end desktop markets, as well as the niche market of fast "gaming panels."
- VA, or Vertical Alignment, delivers good viewing angles and black levels. The term "VA" refers to a number of similar technologies including MVA panels from several manufacturers, and PVA panels from Samsung. The black levels afforded by VA panels is usually seen in their advertised contrast ratios, typically above 500:1. Presently, VA panels are expensive, and occupy the midrange and higher-end desktop display markets, generally with panels 19" and larger.
- IPS, or In-Plane Switching, tends to deliver the best viewing angles, and tends to be the most expensive. IPS panels are produced by several manufacturers, including LG-Philips. Presently, IPS panels can be found in the same markets as VA panels -- midrange to high end desktop displays, generally 19" and larger.
Some cheap, and some not-so-cheap TN panels offer colors at only 6 bits per subpixel / 18 bits per pixel. Video cards and software all expect to work with 8 bits per subpixel / 24 bits per pixel, the discrepancy can cause adjacent patches of slightly varied colors to appear identical on such monitors. Rather than just using 8-bit DACs, there is apparently some reason that the manufacturers of these monitors keep the 6-bit DACs and solve the problem in the controller with a technique they call Frame Rate Control. With FRC, the panel will periodically pulse lighter and darker shades to simulate a midtone.
In their present forms, VA and IPS technologies appear to be largely interchangeable, with minor differentiating strengths and weaknesses. Some specific applications tend to favor one over another, but marginally. This trend may be only temporary due to the prices and rates of innovation. The openness of the debate over which technology is better, along with the expense of the panels may inspire certain individuals to choose a side. When reading a review of a monitor touted as either VA or IPS, try to pay attention to any prejudice of the reviewer.
Reviews will typically include results from colorimeter tests. They will display a graph with red and blue lines, and legends with terms like "delta E" and "delta T." This form of the test is nothing more than a measure of the evenness of gray levels. CRTs with worn phosphors will show their age here, and LCD panels with poorer black levels will show anomalies for the darker grays.
Occasionally, reviewers will take measurements of the response times themselves, often covering transitions to/from a range of grays or colors. This can be very enlightening, provided that at least one reviewer performs this measurement on a model you are interested in.
Some reviews, such as those on Tom's Hardware, even include uniformity measurements of the backlighting.
Review sites:
- BeHardware/hardware.fr, while slightly less professional, has some very extensive discussions about LCDs, and reviews of less common monitors. This site has a bias toward VA panels.
- X-Bit Labs has a good breakdown of the technologies, along with regular categorical reviews. This site has a bias toward IPS.
- Tom's Hardware has a very detailed standard review process for LCD monitors that covers a lot of important details, and a few silly things.
- FiringSquad, a site devoted to first-person-shooter games, focuses on monitors for this task. They have a recent review of 19" monitors.
- C|Net reviews everything, including monitors, and reviews lots of monitors. Some have pretty flash videos. However, their standard for reviews seems flimsy and shallower on details than the above sites.
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