The three general LCD panel types, roughly in order of increasing quality, are: TN, MVA/PVA and IPS.
TN panels- The most common in today’s market. They typically boast very fast response times, and as such are usually easily recognizable by being marketed as “2ms!!!!11” or “5ms”.
However, they are notorious for having very bad viewing angles. Every move to the side or top of an LCD screen and have the colors all inverted and messed up? That’s a telltale sign of a TN panel. This is typically specified as 160° viewing angles, whereas LCD panels built using a higher quality technology will typically be specified as having viewing angles in the 170° range.
Additionally, TN screens are known for having bad color reproduction quality — although I’m no longer entirely up to date whether this is still necessarily the case. Fact is, though, that at one point in time (not too long ago; max. a few years), TN panels typically use 6-bit color channels instead of the regular 8-bit color channels.
This means that TN panels could display only 2^6 = 64 shades of red/green/blue natively, as opposed to 2^8 = 256. As a result, TN panels can display only 262,144 colors naturally instead of the full 16,777,216.
Naturally this wouldn’t look very good, so they compensate for this somewhat; but you can still usually tell by some degree of horrible banding. What they do is employ a technique called dithering to fake intermediate colors by rapidly switching between two adjacent shades. The telltale sign for this used to be that these screens would be marketed as displaying “16,2 million” of colors as opposed to the “16,7 million”, but for some reason they stopped doing that now; so either TN panels are 8-bit now, or marketeers are simply lying.
Furthermore, TN panels tend to bleed backlight and are rarely uniformly lit. Ever sit in front of an LCD screen in a dark room while it’s displaying an entirely black screen and see its edges glow slightly? That’s the backlight bleeding through. Or see sort of “spots” where it’s brighter than the surrounding area? That’s its non-uniformity.
So I would definitely not recommend you get a TN if you’ll be doing any kind of work in which color fidelity has any importance at all. Sometimes spotting a 20″+ TN screen is easy enough as simply sitting in front of it while it displays a solid color, because the difference in viewing angle between the center of the screen and the edges is already enough to cause a color shift.
TNs are good for gaming though. The technology inherently has very quick response times, making it a good choice for gamers. They are also usually cheap and have little to no input lag.
MVA/PVA-These LCD panels built in an entirely different way from TN panels. They are virtually always 8-bit panels, and as such have noticeably better color reproduction than TN panels. MVA/PVA panels also typically do not suffer from excessive backlight bleeding.
Because of the different construction technology used, the viewing angles are also far better, typically specified as in the 170° range; there will still be slight color shifting when moving to the side of the screen, but it’s nowhere near as bad as TN panels.
On the downside, they are usually more expensive than TN panels. Another problem inherent to MVA/PVA panels is that they typically do not have very high response times — I guess it’s inherent to the production process somehow.
Manufacturers compensate for the slow response times by using what is called overdrive; basically, when an LCD pixel needs to change color, they apply voltages higher than usual to make it shift color faster. When done right, this does actually help to reduce the response time. This is usually marketed as 5ms, 6ms or higher response times.
However, if not tuned right, you get the very nasty effect of ghosting, as was extremely evident on my first ever PVA panel, a 24″ Dell 2407WFP-HC. I’m not an engineer, but from what I’ve read it comes down to the pixels rebounding from a too high voltage being applied to them, causing the black blur behind moving objects.
If you intend to buy an MVA/PVA panel-based LCD screen, you should do your homework on this issue and see if there any reports of ghosting, as it will save you a lot of headache.
Another problem MVA/PVA screens typically suffer from is input lag. This is basically an issue of the electronics surrounding the panel doing too much signal preprocessing, or doing it too slow. The result is typically a slight delay between eg. moving the mouse and seeing it move on the screen. It’s usually just large enough to be noticed but not large enough to be really obvious, causing you to sort of wonder whether you’ve gone crazy all the time.
People have different sensitivities to it and it’s a matter of what your threshold for noticing it is, but for me it was evident on the 2407WFP-HC which had it in about the 30+ ms range if I recall. I’m currently using an MVA panel which has 21ms and I don’t notice it at all, so it’s really a matter of finding your cutoff. It’s hard to find a *VA panel with input lag as low as 20ms though (I have the LG L245WP).
IPS panels-There are various subtypes of IPS panels, most notably S-IPS and H-IPS, but their properties are largely similar. H-IPS is the newer technology and fixes some issues with “sparkly” blacks on S-IPS panels, so grab it if you get the chance.
IPS panels are about the best LCD panels out there when it comes to color reproduction quality. They are typically used in high-end contexts, such as medical imaging and computer graphics professionals.
They have a minimum color depth of 8 bits, but depths of 10 or even 12 bits are not unheard of. As such, color reproduction quality is the best you’ll find out there, displaying no gradient banding or color shifting.
IPS panels are also known for having unparallelled viewing angles. IPS panel colors stay the same no matter your viewing angle. As such, it’s often times used in smaller screens for which such properties are desirable, such as cell phones and (non-junk) digital photo frames.
Pretty much every portable Apple product uses them by the way (marketed as Retina displays now I think), as well as the larger iMacs. It’s no coincidence that Macs are typically used for graphic design.
IPS panels also exhibit at least some form of input lag, but it’s usually low enough to be unnoticeable (usually somewhere around 12ms-20ms).
Unfortunately, IPS panels are the most expensive screens there are.
