Slashdot Mirror
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."
These terms 'response time' and 'contrast ratio' are checklist items. What matters is how the display looks and feels. As long as we continue to insist on checklists as a means of determining what to buy, manufacturers are going to keep using tricks like overdrive to make their checklists look better and better.
At the end of the day, sadly, this means that you can't just look at a checklist when buying an LCD display. You must test drive a model live before considering its purchase.
My blog
reminds of my time making CDROM drives when we ere chasing 4x, then 8x, then 16x, then...
never mind the fact that the interface at the time could not handle the high speeds were were getting too so they were totally pointless, the effort was still to physically read some data off the outer edge of the disc at the quoted speed so we could sell the unit and keep up with the arms race.
I now purposely buy technology a few years old, just so they can work the bugs out and I can ensure it is fully supported under all operating systems, it is rare indeed that I adopt early.
any technology arms race will promote one specific feature above all others and rarely end up with a device that is fit for market and a well rounded balance of features - though I grant that there are some exceptions.
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
No, plasmas have near instantaneous response times that are pretty much identical to what you get on a CRT. The issues you get with a plasma is called "phosphor lag" which has to do with the three colors not quite lining up perfectly and it gives you a trailing image of the colors. It's especially noticeable on high contrast edges or if things are moving really quickly. It can be especially noticeable in gaming, but at least IMO it's much less annoying an artifact than the ghosting, smearing, and horrible motion resolution you get with LCDs (and yes they are present even on 120hz LCDs before someone brings that up).
I knew somebody would make some gross misstatement like "The human eye only sees at 25 fps anyway"
And for that, here is the obligatory link to 100fps.com
In short, the shortest flash a human eye can see depends on a lot of things. These factors are explained thoroughly on that web site. The tl;dr version is this: The human eye can discern A LOT MORE than 25 fps.
Buying an LCD is becoming a real pain in the arse.
Perhaps, but buying a CRT was a real pain in the back.