Input lag: How important is it?

CNET's measuring input lag, but how important a measurement is it?

Sarah Tew/CNET

Recently, CNET started measuring input lag. This is the amount of time it takes for a TV or projector to produce an image. In the worse case, excessive input lag can cause lip sync issues. In most cases, it can lead to worse performance with certain games.

Since the article hit, there's been a surge of people ridiculing certain displays as "unacceptable" due to their input lag issues.

Hang on -- unacceptable? Just how important is input lag, anyway?

OK, first, what's input lag? As mentioned, it's how long it takes for a TV to create an image. This includes processing like deinterlacing, scaling/upconverting, frame interpolation, and more. With movies and TV content all you might see, at worst, would be lip-sync issues, but this is fairly rare.

With games, however, this additional lag can be a serious issue. Adding 50 to 100 milliseconds between when the enemy is created by the game, and when you see the enemy (and press the button to shoot) can be the difference between getting shot in the face and not. On the Web, with multiplayer games, this is even worse, given that there's already a 50-to-100 millisecond (or greater) latency between your console/PC and the game's server. Add these two kinds of lag together, and you're way behind.

As a gamer myself, I can definitely notice the difference in lag of 50 and 100 milliseconds between me and a server (latency). When I played more, I could even tell the difference between 20ms and 50ms servers. I noticed a big hit in my personal performance when I moved from a CRT monitor to a projector in my theater. Same game, same person, way worse scores. Turns out this was almost entirely do to the greater input lag on the projectors. So this isn't, as some have said, strictly the purview of professional gamers. Even "enthusiasts" could notice the problem.

So it would seem clear cut that lower input lag televisions are superior for gamers, right? Well, it's not nearly as simple as it would first appear.

Please increase your lag, for a moment
First of all, not all gamers need low input lag. The only time you'll really notice it is with twitch games like Call of Duty, Planetside 2, Battlefield 3, and other first-person shooters. With most other games, such precise timing simply isn't required. Sure there can be some cases where you need to launch a certain spell in WoW or Guild Wars 2, but the window to do so is far more forgiving than with first-person shooters. Really bad lag can be noticeable in other games, but in the lag range of most "good" TVs we've been getting tweets, comments, and e-mails about aren't bad enough to be considered bad.

Take, for example, one of our favorite TVs this year, the Panasonic's ST60. It has an input lag of 73.6 milliseconds. Is this a lot? Is this noticeable? Could be. Is it worse than Panasonic's cheaper S60? Yes, by 39.5 ms. But it the ST60 looks better, and that's the part we should focus on.

Picture quality is the most important aspect of a television, right? I mean, the point of a TV is to look at images on it, so it stands to reason that how good it's able to do that would be critical.

Also, let's look at what we're talking about here. The Sony KDL-55W900A got an 8/10 for performance, and has an input lag of 19.7ms. The Panasonic TC-P55ST60 got a 9/10 for performance. Remember, though, "0" ms isn't a starting point, sadly. Yes, the ST60 adds 73.6ms of lag, but the best you can hope for (right now), with somewhat similar picture quality, is 19.7. So, it's really a 53.9ms difference. Is 53.9ms worth the hit in performance and the much higher price? That's a judgment call that's entirely up to you. Personally -- and remember, I'm a gamer -- I'd rather have a better looking image with slightly more lag. But that's me. I'd also be happy with a Game mode that worked well enough, for the times I wanted less lag.

Then there's motion blur. Many of the lowest input lag TVs are 60Hz LCDs models that are going to blur significantly with any motion. So sure you don't have as much lag, but if the image is blurred and you can't see the enemy, who cares if there's no lag? Check out What is refresh rate? for more info.

Now keep in mind, if your goal is to have the lowest input lag, that's different. If low input lag is paramount for you, then picture quality is, by nature, second. But that's a specific use, and not what most people are looking for.

Bottom line
If your goal is to be at the top of the leaderboards in CoD, BF3, or whatever, then absolutely get the display that has the least amount of input lag. This is, typically, a computer monitor or a minimally featured LCD (and some plasmas). But if you want the best picture quality you can, but with considerations for input lag, that's going to be a different TV. Maybe one with a Game mode. If you're a gamer, how much lag versus overall performance is something subjective to you and you alone. It's worth noting that we consider anything below 40ms as "Good," 40 to 70ms as "Average," and anything higher as "Poor."

We all want input lag to get lower, which is one of the reasons why we've started measuring it. But even though input lag can be important, keep in mind it's still just one aspect of overall performance (and nowhere near the most important). Even if you're a gamer, it's not nearly as cut-and-dried an issue as it first appears. If all you want is a high score, then that's one thing. But if you want to enjoy looking at the game you're playing, enjoy the graphics and the art design of the game, then perhaps a slight lag penalty is worth it.

Hopefully, eventually, there won't be this choice between low lag and ultimate picture quality.

If you're a gamer, what's your take? How much lag, versus how good a quality of picture, is your personal trade-off?

Got a question for Geoff? First, check out all the other articles he's written on topics like HDMI cables, LED LCD vs. plasma, Active vs Passive 3D, and more. Still have a question? Send him an e-mail! He won't tell you what TV to buy, but he might use your letter in a future article. You can also send him a message on Twitter: @TechWriterGeoff.

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