Hello everybody. I keep seeing repeated questions about input lag, so I thought I'd do up a guide to help people understand it, know how to test for it, and know if it really matters to them. And maybe refer back to this link for people asking about the question in general. What is Input Lag?
In simple terms, Input Lag is any delay between a signal being sent to your TV and having it displayed on your screen
. Most TVs have input lag. This lag is not noticeable when watching video, as the TV knows about the lag and syncs the audio to match. However, when you're interacting with the TV (ie controlling what's displayed), this delay can become noticeable.My TV lists an 2/5/8/etc ms response time. Is that the input lag?
No. This is a common misconception. Response time is the amount of time it takes for a pixel to shift its color. This can help prevent blurring or ghosting in your picture, but has nothing to do with input lag. Virtually no TV maker lists input lag on their product material.What causes Input Lag?
The primary cause of input lag is signal processing. Anything that requires your TV to alter the signal it receives can delay the transmission of that signal to the screen. Processing comes in three general varieties:
A) Inherent lag in the circuitry of the TV, which can't be removed.
B) Image scaling. If the TV receives a signal that it doesn't natively support, the TV has to scale the image to fit its display. For example sending a 720p signal to a 1080p TV will cause input lag, as will being forced to deinterlace a signal.
C) Postprocessing: Anything that a TV does to a signal to "improve" it for the viewer. This includes noise reduction, motion smoothing, dejudder, dynamic contrast adjustment, etc. Most TVs do a lot of postprocessing in their standard modes, which isn't what you want. Most new TVs do have a "game mode" that turns off most, if not all, of the postprocessing features of the set.
So, ultimately, to minimize input lag, you want to:
A) Select a set with minimal base input lag
B) Make sure you feed your set the proper size signal for its fixed resolution.
C) Turn off any postprocessing features you can (either through GAME mode or manually disabling features).How can I find out how much Input Lag my set has?
There are two ways to test for lag:
A) The CRT stopwatch method. CRTs do not lag, so you can hook up a computer with dual display to both a CRT monitor, then your TV, and feed them the same signal with a stopwatch application running. Taking pictures of the two displays side by side will show how far off the TV is. This is a decent method, but has its own pitfalls - it's not always easy to find a CRT and a TV that accept the same native signal. If you output something different from your TV's native resolution, you introduce scaling lag into the equation.
B) Rock Band 2 has a built in input lag tester. Using a copy of the game along with a Rock Band 2 guitar, you can do an automated test. RB2 runs 10-20 seperate tests and then averages the total. This has actually proven to be a better test than CRT, simply because it automates the process, gives consistent results that match CRT tests, and can easily be run at the television's native resolution.
In either case, the time difference or video lag shown equals miliseconds. 16ms = 1 frame of input lag, assuming the game runs at 60Hz/fps.Does the input type I use (VGA/HDMI/Component) matter?
In theory, any connection that can support your TV's resolution can deliver the same response time, but like screen type, this varies from model to model. The short answer is it depends - try any and every HD input your TV has to see if it makes a difference!Does the screen type (Plasma/LCD/RP) matter?
Again, it depends. In very general terms, Plasma sets have better input lag than other types. However, in practice this is HIGHLY variable, as each model TV has varying characteristics. So getting a plasma doesn't guarantee no/low input lag - any set you want to buy should be tested individually.What's the average Input Lag for TVs?
Generally speaking, most decent brand name TVs have 30-60ms of input lag in GAME mode, which is 2-5 frames. With full postprocessing on, the numbers can get pretty high - I've hear of 100+ in some sets.How much Input Lag is acceptable?
Input lag is overblown right now among the gaming community - this is primarily because many older sets had pretty horrendous delays on them.
Anything that is under 48ms (3 frames or less) is going to work fine, even for "hardcore" gamers. That's 1/20th of a second - for comparison the average human reaction time is around 1/5th of a second. The only example I can think of where you might need a better response time is for expert level fighting game players, because some games have combos that require inputs in specific 16ms windows.
Most people don't notice a difference until about 50+ms of input lag, which is 4+ frames, and gets progressively easier to notice the higher you go. Now, I know some people are going to start screaming "I can feel the difference between 2 or 3 frames!", but I can tell you that no, it's highly likely you cannot
. The maker of GGPO (an online fighting game networking protocol), ran tests with pro-level, tournament winning fighting game players. The results showed many of them could not discern any difference between 0 and 2 frames of lag. Chances are good you're not a unique snowflake that has superhuman reaction times. So don't drive yourself crazy trying to find the "perfect" set - there's lot of great options at an input lag level you'll never notice.
That being said, if you believe you're a unique star-child, then feel free to look for the gold standard in lag, which is 15ms or less, which is no frame delay at all. Very, very few sets have been tested to verify this, so be prepared to look for a good long while!TESTED SETS
Sharp LXX77UN: 25ms (Game mode) Personal Testing
Sharp LxxLE700UN: 25ms (Game mode) Personal Testing
LG XXLH90: 45ms (Game mode) Personal Testing
Samsung LEXXA950: 45-60ms (Game mode or VGA port) link link
Samsung LEXXB650: 45-60ms (Game mode) link
Panasonic TCPXXG, and V series: 30ms link
LGXXLH30: 0-15ms (
Any questions, comments, etc, feel free to respond. Thanks!