Response times, what do they do really?

[Opus131]

I own a 27GL850 which is one of the fastest IPS panels out there but also comes with the lowest contrast among panels with this type of technology, almost as if they had to sacrifice the latter in order to achieve the first.

I've been mulling over whether returning this one and getting another one with better contrast, but if i did that i'd be sacrificing response times all though as of right now i'm not sure how important this is.

I tried all the overdrive settings on the 27GL850, from off to fastest, and honestly i can't tell any of them apart. Now, in my ignorance it was always my understanding that response times meant the monitor was going to be snappier, but, that is not the case? I'm now hearing that all it does is reduce motion blur depending on the frequency, and there's a "set" amount of ms you need at each frequency point after which i presume there really isn't much of a difference?

For instance, i read you need 16ms or lower for 60hz and 7ms or lower for 144hz. Now, i checked the 27GL850 and apparently it has a whopping 6ms with the overdrive set to off, 4ms at fast and 1ms on faster. Since even the lowest setting is below the threshold needed to removed motion blur at 144hz, is that maybe why i can't tell the difference between off, fast etc, or is there more to this?

Right now i'm considering the Asus Tuf model:

https://www.rtings.com/monitor/tool...-lg-27gl850/1640/912?usage=3623&threshold=0.1

Which has an 100% response time of 10ms, which is above the 7ms you need for 144hz, let alone 165hz. But it also has a solid contrast ratio (for an IPS screen) of 1250 circa. The black insertion thingy makes the monitor flicker from what i understand so that's not something i would be using, so it's a toss up between motion blur and contrast. I know it all depends on personal needs but i happen to need both all though i'm not entirely sure which would annoy me the most. I know the low contrast of the 27GL850 annoys me, but it is possible to partially fix that using a bias lighting or by playing around the brightness (brightness set to zero actually offers a good results, but that forces you to raise the contrast in order to elevate the luminance of the monitor and that sometimes leads to weird effects). Motion blur, i'd have to see it to really judge whether i'd rather do with one or the other.

Apart from that, the 27GL850 also seems to have better colors so it feels like it's an all around better monitor, but not exactly an "all rounder", given that it sacrifices one thing to improve another. I'm guessing this is aimed more at trying to make TN redundant as opposed to making IPS a more "complete" technology.

 

[kalston]

Response time is simply how fast pixels can switch their color (since LCDs can't do it instantly). So yes, lower response time = sharper image in motion, less motion blur. But you still keep the sample & hold motion blur natural to most display techs unless using some form of strobing/BFI (and at 60hz, the motion blur is massive). It's true that your monitor has sufficiently low response times for the refresh rates it can handle - so there are diminishing returns there - but it still helps a little bit because it reduces visible artifacts (a cleaner blur we could say). Explained there: https://www.blurbusters.com/gtg-versus-mprt-frequently-asked-questions-about-display-pixel-response/

The settings of your model are described in depth here : https://www.tftcentral.co.uk/reviews/lg_27gl850.htm

Basically some transitions are faster than others, but IPS and TN behave nicely nowadays and it's only on VA panels that it is big issue. On IPS or TN the average gtg as measured by reviewers (forget the number given by the manufacturer, it's almost always a joke) gives a very good idea of what to expect.
An issue that creeps up especially with the higher overdrive settings is "reverse ghosting" or "overshooting", basically trailing in front of objects as opposed to behind them - the algorithm tries to predict motion but fails.

 

[Opus131]

So i suppose the reason i can't tell the difference between off and fast is that this difference is too minimal (6ms vs 4ms) where the 1ms fastest setting adds so many artifacts that any advantage i may be able to see is obliterated by the ghosting/smearing.

With that said, i WOULD be able to tell the difference if the response time was 10ms or 14ms like a VA, right?

 

[Sancus]

With that said, i WOULD be able to tell the difference if the response time was 10ms or 14ms like a VA, right?

VA's problem is not average response time, it's that the dark transitions sometimes take as long as 40-50ms, which produces very obvious dark smearing. This is sadly the case even with the best, most expensive VA panels out there. On average, its response times are fine.

I own a 27GL850 which is one of the fastest IPS panels out there but also comes with the lowest contrast among panels with this type of technology, almost as if they had to sacrifice the latter in order to achieve the first.

It's impossible to tell why the 27GL850 has poor contrast, but it's not that the response times are that fast, it's that they're that consistent. The Innolux panel has just as good response times -- but only at 144hz, not at lower refresh rates.

There are basically 3(good) options for high refresh 1440P 27" displays.

LG: (27GL850) - Good response times at all refresh rates(~5ms), so no need for variable overdrive. Poor contrast(800:1).
Innolux: (Viewsonic VX2758-2KP-MHD, Gigabyte AD27QD, etc) - Good response times only at 144hz, but very good contrast(1200:1).
AUO w/G-sync: (PG279Q & XB271HU) Fast, and good(for IPS) contrast(1100:1). Uses variable overdrive to achieve this with G-sync module. Not as good as the other two panels when used in a Freesync display a la Nixeus EDG.

If you're going to worry about these kinds of incremental differences, why not just buy a G-sync monitor and call it a day? They have response times as fast as the LG, with significantly better contrast. Freesync options have just been chasing the G-sync benchmark for 5 years.