StupidBlur wrote:About the IPS, 4ms is too high unfortunately. Not sure if I would actually notice it, but id rather have 1
Some 4ms IPS monitors have less input lag than 1ms TN monitors.
True, there is sometimes the processing lag in the TN monitor.
However, on the topic of GtG:
RealNC wrote:The 24GM77 has a pixel response time of 7ms (the "1ms" you see in official monitor specs is just marketing and doesn't represent pixel response in real-world use.) The total input lag of that monitor (pixel response + signal processing) is 32ms without DAS, and 18ms with DAS.
Keep in mind that humans will generally respond before the end of pixel response time. e.g. GtG only needs to move partially before it gets human-noticed. Even back in the 33ms monitor days, pixels were somewhat visibily half-transitioned by roughly 8 or 16ms for example. Yes, it smeared like hell, but humans begins the reaction-time clock well before the end of pixel transition completion (GtG fully complete).
With high speed camera tests, enough transition occurs to become human-noticeable after approximately ~0.5ms from the beginning of voltage being injected into the pixel of the transition on most modern TN LCDs, even if there's still some ghosts that persists for much longer such as 7ms. That said, the monitors with almost zero strobe crosstalk (Say, the ASUS VG248QE with LightBoost) manages to do over 95% of GtG transitions within the first 1-2ms.
Industry standard GtG benchmark is timed from 10% transition to 90% transition.
For a fullblack to fullwhite transition (color level 0 to color level 255) --
that means a black pixel is already now a visible dark grey (~RGB(25,25,25)) when GtG begins to be benchmarked, and becomes nearly completely white (~RGB(230,230,230)) when GtG finishes being benchmarking, long before it's at color level 255.
It can also be horrendously nonlinear depending on panel tech, and depending on color pair. There are times where GtG(1%-99%) can be 24ms, while GtG(10%-90%) can be 1ms. The better the overdrive in cleaning up GtG overshoot/undershoot as quickly as possible, the more accurate it is. A display can even have a narrow spread -- e.g. GtG(1%-99%) 10ms and GtG(10%-90%) 4ms.
Photodiode input lag tests is sometimes measured into the early part of GtG (when it becomes visible), or at worst, approximately 50% --
roughly halfway into GtG. Even that is not a bad compromise, given human will react well before GtG has practically fully (>99%) completed.
After whatever processing -- once the voltage finally hits the pixels, most "1ms TN" panels have almost identical human reacting-to-it times (after voltage hit) regardless of GtG measurements, due to various nonlinearities. Almost all of them show visible response (enough GtG partial completion to become visible) within 1ms of the pixel actually being voltaged, even if the end-momentum of GtG90% or GtG99% varies a lot (2ms, 7ms, 20ms, whatever). You actually have to switch panel technology (e.g. IPS) to see a much more noticeable difference in human-noticeability-at-beginning-of-GtG.
A basic GtG measurement such as GtG10%-90% doesn't explain how fast GtG10%-20% or GtG30%-70% or GtG80%-90% is -- it can be a quite nonlinear curve that's faster at the beginning or faster at the end, heavily depending on the overdrive algorithm and what color pair is being done. So simpler is to measure via photodiode or high speed camera, to more represent beginnings-of-human-visibility.
Indeed, you're right -- a hugely overriding lag determinator will be processing overhead -- e.g. how the monitor processes the signal or does real-time ("instant") scan-out like a proper gaming monitor does. Factors like that can definitely make an IPS monitor have lag than TN, despite having slower responding (GtG) pixels
Regardless, this is a good consideration about input lag. The 24GM77 does realtime scanout AFAIK. So does ViewSonic (At least according to Leo Bodnar lag tester -- a photodiode type test). Less than 1ms difference between the LG and ViewSonic according to DisplayLag(.com).