Input lag...

H

Hudder

Weaksauce
Joined
Jun 6, 2007
Messages
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I'd like to see a discussion of input lag outside the thread regarding gaming.

What causes input lag? Is it panel type? Is it overdrive circuitry? What else? What models are bad, what are not? Why are manufacturers only listing response time specs, and no input lag spec?

Also, please share any links to write-ups about this specific issue.
 
Input lag typically only happens when the internal scaler has to do something. Input lag is usually only noticeable on interlaced content like 480i or 1080i. So that only applies to monitors with tv/s-video/component inputs or lcd tvs. Some processing has to be done if you do stuff at non-native res, to scale the image to full size, but most graphics cards will take over the scaling anyways.

Anyways it is mainly an issue with LCD TVs because they have to deal with sources that need to be scaled and deinterlaced.
 
Correct me if I'm wrong but here's what I've surmised about input lag (reposted from where I posted this in that gaming thread)...

Input delay is caused by any extra processing the monitor has to do before showing a frame on your LCD.

The less processing an LCD has to do, the faster it will display each frame.

Things that can require processing (please correct me if I'm wrong here):

6-bit pixel depth can require processing to "fill in" the color range and to translate from the 8-bit signal it got from the video card - often times monitors make up for the ~200,000? color range by making certain colors brighter, etc.

Stretching, improper scaling, etc: basically, if the monitor doesn't do natural scaling and supports multiple resolutions besides its max res (i.e., most good monitors today now do this, and can display multiple resolutions very sharply without blurring or distortion), then it's processing a little to fill in a lower res across all of the display.

The signal processor: simply put, the tech that translates a signal from the video card into a signal going to all of the pixels on the LCD. These seem to be getting faster these days, and I'm pretty sure each one can be slightly different on each monitor depending on what technology is being used.

All in all, I'm pretty sure that you could line up a row of every type of panel, and the one with the least amount of input lag would probably come down to whichever panel was displaying things as natively as possible without having to do any extra work before each frame was displayed.
 
Interesting ZeeN. One of the things I have found a tiny amount of info relating to input lag is overdrive circuitry. This is used to prevent ghosting, and would be processing, right? Do you or anyone else know anything about it?
 
Hudder said:
Interesting ZeeN. One of the things I have found a tiny amount of info relating to input lag is overdrive circuitry. This is used to prevent ghosting, and would be processing, right? Do you or anyone else know anything about it?
Click to expand...

Overdrive circuits are used by a lot of LCD TV manufacturers because in essence, a liquid crystal will transition faster when put under more voltage. It will transition slower under lower voltage. If the voltage is too high in the overdrive circuitry then you should see bright artifacts around moving objects. If the voltage is too low I guess you see dark artifacts. Trippy, huh?

That's all that overdrive circuits are, to my knowledge.
 
From what I've experienced and seen, TN panels don't seem to have input lag that often, while among other (better panels) it's rather common. It is not the panel however, but the electronics inside. So if you're buying a gaming display you'll most likely buy a TN anyway so no worries.
 
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