Input Lag, Or Why Faster Isn't Always Better

mr_sifter writes "LCD monitor manufacturers have constantly pushed panel response times down with a technique called 'overdrive,' which increases the voltage to force the liquid crystals to change color states faster. Sadly, there are some side effects such as input lag and inverse ghosting associated with this — although the manufacturers themselves are very quiet about the subject. This feature (with video) looks at the problem in detail. The upshot is, you may want to test drive very carefully any display boasting low integer millisecond pixel response times."

Comments

Another thing to look out for

[Hyppy]

First, we have to look for monitors with 6bit or 7bit color instead of 8 per channel, now we have to start testing for overdrive voltages? Buying an LCD is becoming a real pain in the arse.

Re:Another thing to look out for

[Elledan]

6-bit TN panels don't seem like such a good idea to me, as the interpolation (rapid cycling of pixels to get the desired colour) used to compensate for the lack of full 16.7 million colours other screens have is (together with the flickering of CCFL backlights) responsible for most of the complaints about LCD screens giving people a headache.

As for the article topic, any screen with an input lag of >1 ms will never be 'good' at displaying rapidly changing images, and will be nearly worthless for rapidly-paced games. Plasma, CRT, SED, FED, OLED... all technologies with sub-1 ms latency. Getting that 15" OLED screen LG will be releasing this year as a monitor may not be such a bad idea. Sure, it's not as big as your 24" LCD, but it will have perfect colours and blacks, extremely low-latency, low power-usage, weigh even less than an LCD, and so on.

Let's admit it, LCDs were just an intermediate technology for displays as margins in the CRT market got lower and lower, while new display technologies which could match or beat CRTs in IQ and other factors were still a while off.

Reason for input lag

[Rotaluclac]

The reason for input lag is that manufacturers want the on-screen image to quickly change without ghosting. Here, quickly means "in as few ms as possible", not "without delay". So if you see a change only two seconds later, but the change is instantaneous, that's considered good.

To achieve this, the display electronics must know what the next frames look like. So they buffer two or three frames, then adapt the overdrive on a per-pixel basis to the contents of the next few frames.

Pro: smoother video playing
Con: a delay of two or three frames

Rotaluclac