Is there any way to know the input lag of an LCD?

[SenorBeef]

Apparently LCDs have a delay of tens of milliseconds before the image sent from the video card is actually displayed on screen. This is seperate from pixel response time - it has to do with the monitor taking a short while to compose an image before it’s displayed, sort of like a frame buffer. So there’s a small delay between taking an action like moving a mouse and the resulting visual effect on the monitor of your action.

This seems like it would be disruptive to games that require fast reaction time.

Do different monitors have different input lag times? Manufacturers don’t list “input lag = 23 ms” or anything on their specs, so if they do differ, how do you find out which ones have the least?

[Gfactor]

I’m going to go ahead and assume you didn’t intend to post this as a reply in the What exactly is the military rule on homosexuality? thread. I made it a new thread.
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Gfactor**
General Questions Moderator

[Absolute]

I am not aware of anyone publishing specifications on this, because the delay is too short to be noticeable. Certainly shorter than the physical delay of the LCD pixel refresh - which is published.

[Jragon]

Monitors do in fact have differing input lag. Part of it has to do with native resolution. A monitor meant for 1680x1050 may have a more sluggish response at 1280x768, because it has to “stretch” it.

The reason they don’t show this is because, well for one the difference in different resolutions, but also because it’s ridiculously hard to measure. I don’t feel like typing it up so here’s what our good friends at wikipedia have ot say:

Input lag is easier “felt” than seen. As such, proving the existence of this phenomenon requires an elaborate setup (at least for a home computer system). Tests for this phenomenon usually involve a test display (the display being measured), a control display (usually a CRT) that would ideally have no input lag, a computer capable of mirroring output to two displays, stopwatch software, and a high-speed camera pointed at the two displays running the stopwatch program. The lag time is measured by taking a photograph of the displays running the stopwatch software, then subtracting the two times on the displays in the photograph. This method only measures the difference in input lag between two displays and cannot determine the absolute input lag of a single display. CRTs are preferable to use as a control display because their input lag is typically negligible. Also, video mirroring does not guarantee that the same image will be sent to each display at the same point in time. However, since the results of this test are easily reproducible, even when the displays are plugged into different ports and different cards, suggests that the effect is attributable to the display and not the computer system.

So teh only way to tell is to find someone with nothing else to do online that’s nice enough to set up this crazy contraption and give you teh numbers.

[SenorBeef]

@Gfactor

I’m going to go ahead and assume you didn’t intend to post this as a reply in the What exactly is the military rule on homosexuality? thread. I made it a new thread.
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Gfactor**
General Questions Moderator

Yeah, that was strange. I did create a new thread, and I hit post, and it took several minutes to actually post. When it did post, it was a reply to an unrelated thread. Huh. Thanks.

@Absolute

I am not aware of anyone publishing specifications on this, because the delay is too short to be noticeable. Certainly shorter than the physical delay of the LCD pixel refresh - which is published.

An article I was reading did a recording of two monitors with timestamps on them. They found the particular LCD they were testing on was generally 47ms behind the CRT - that’s significantly more than the pixel refresh time which can get down below 5ms.