Does non-native Hz effect image quality?

Talk about overclocking displays at a higher refresh rate. This includes homebrew, 165Hz, QNIX, Catleap, Overlord Tempest, SEIKI displays, certain HDTVs, and other overclockable displays.
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Irlwizard
Posts: 16
Joined: 17 May 2015, 05:51

Does non-native Hz effect image quality?

Post by Irlwizard » 18 May 2015, 04:45

I know from tftcentre reviews (example: http://www.tftcentral.co.uk/reviews/benq_xl2720z.htm) that if you change a monitor from e.g. 2500x1000 to 1900x1000, even tho you DOWNGRADE the resolution (perhaps so you can run a new title at 60+ FPS), the picture quality is REDUCED, this is very evident when viewing text - a lot of sharpness is lost. I think the term is called 'interpolation' but I could be wrong.

This also seems to be the case when you change from e.g. 16:10 native to 16:9, 4:3 or any non-native aspect ratios.

Is this bad picture quality also true when you have a 144Hz rated monitor... That is actually built to run 120Hz as its NATIVE Hz. But the manufacturer has OCd it to 144Hz so they can sell it for more. So in this example the monitor has a native 120Hz, if you play on it using 144Hz, 120Hz or 75Hz (maybe 75Hz for Metro Last Light or something graphics heavy). Will the picture quality alter in any way? From colour accuracy, to gamma, brightness, sharpness or even input lag? Especially on still/fixed objects such as text. When the monitor is set and played above or below the 'native' 120Hz range?

Falkentyne
Posts: 2793
Joined: 26 Mar 2014, 07:23

Re: Does non-native Hz effect image quality?

Post by Falkentyne » 18 May 2015, 14:18

Well, usually, no.
First I'll say this.
No monitor in existence is designed to be 144 hz native. 144 hz refresh rate does not even use standard timings (if you attempt to create it manually using normal timings, e.g. for 120hz, it will go out of range).

In fact, If I may be bold, I'll say that every LCD is actually BEST at 60hz for image quality.
On SOME monitor panels, you won't suffer a loss of image quality from going from 60hz to 120hz, or even bizarre refresh rates like 75hz, 85 hz or 91 hz. However, on many panels (the M240HTN01.0 panel used in many "1 ms" 120/144 hz gaming LCD's was VERY notorious for this), increasing the refresh rate past 60 hz would degrade image quality. Usually delta changes, gamma would get reduced (image would get washed out) and color fidelity would decrease. Most of this could be fixed by a calibration for the specific refresh rate.

On some samples, you may even begin to get a scanlines effect on the screen (usually very faint) as you get towards 120/144 hz refresh rate.

Irlwizard
Posts: 16
Joined: 17 May 2015, 05:51

Re: Does non-native Hz effect image quality?

Post by Irlwizard » 27 May 2015, 22:00

Falkentyne wrote:Most of this could be fixed by a calibration for the specific refresh rate
So if a monitor that can run 144Hz was calibrated on 60Hz, 120Hz and 144Hz. The image quality would be the same on all settings IF YOU OWN A GOOD CALIBRATION TOOL. Is that right? If not, how much is colour accuracy would be lost between 60 and 120Hz (e.g. 15% on a 2014+ gaming monitor)?

I don't want to use light boost, I hate all flicker tech. But I am tired of 60FPS and tired of input lag. Plus, how would you calibrate Gsync because the FPS can range from maybe 60-144 depending on how busy the ingame scene is. Would you calibrate it for 144Hz and accept a loss of quality on the lower FPS or the other way around? Gsync sounds dumb for picture quality and colour accuracy.

What is my best option to get a colour accuracy (picture quality)/smoothness (no tearing)/lagfree experience (low input lag)? Without using light boost.

Would it be better to Vsync (with or without triple buffing) at 120FPS with a GTX980 on a native 120Hz VN/TN panel or just get a 144Hz Gsync monitor with a GTX970? The price save by not going Gsync can be put towards a stronger card that allows you to Vsync at high frames. Even if you drop below 120FPS and your Vsync is halfed from 120 to 60, 60 is still more than enough as it is already a old 'standard'.

Falkentyne
Posts: 2793
Joined: 26 Mar 2014, 07:23

Re: Does non-native Hz effect image quality?

Post by Falkentyne » 27 May 2015, 22:31

Unfortunately, your question can't be answered because every single panel is different.

Some panels keep tight and accurate color and gamma curves and response at all refresh rates (from 50 to 144 hz, maybe only deviating by 0.1 gamma or a tiny delta). (the Benq XL2720Z is like this; AU optronics M270HTN01.0). But a different panel might drop from 2.2 gamma at 60hz to 1.9 gamma at 144 hz (a very famous and popular example is the workhorse 1080p 24" panel, AU Optronics M240HW01 V8, which is used in a large number of 1ms gtg 144hz panels, like the Asus VG248QE, Benq XL2420T, XL2420TE/TX, XL2411Z, 2420Z, 2430T, etc all tend to do this).

It doesn't directly matter which OEM makes the electronics for the scaler and OSD (e.g. Acer, Asus, LG, Benq)--what matters is the actual panel itself--the part number. The default gamma is set by whatever the OEM's program into the scaler. This tends to apply at least as far as gaming panels are concerned. Some very expensive (e.g. non gaming) panels have extra circuitry to compensate for any sort of image dropoff by automatically recalibrating itself or allowing full onboard (not windows based) calibration.

There's no panel database that tells us what panels are susceptible to degradation or washout at higher refresh rates and which aren't. Only user feedback and self use and trying to ask questions about panels people own can answer these things.

I own the XL2720Z and I use motion blur reduction all the time (I never turn it off) so I cant really tell you what you should get. At this point, I'd recommend any Gsync monitor if you have an Nvidia panel. If you want to push high frames, no current single video card can maintain 144 fps at max details on a 1440p screen. Even 1080p is pushing it if you max out the details in anything recent. And you're going to get stutters if you don't use Gsync. It is noticeable and it helps massively. Now IF you can always keep 120 fps at 120hz all the time, then using ULMB, Benq blur reduction or any other strobe tech will give you a more enjoyable game experience (after all, having NO motion blur is better than having blur). You cant use both motion blur reduction tech and Gsync at the same time together (even though they can both be in the same screen, strobe tech is currently incompatible with variable refresh rate.

All gsync really is, at this point, is a combination of

1) variable refresh rate (dynamic refresh rate)
2) vertical sync
3) Triple buffering.

stutters are removed by the refresh rate always matching the framerate--all the time.
tearing is removed by vsync being always on.

that's simplifying it to the extreme, but that's basically what it is, in a nutshell.

MrBonk
Posts: 11
Joined: 27 Mar 2015, 03:55

Re: Does non-native Hz effect image quality?

Post by MrBonk » 12 Aug 2015, 01:51

If you use scaling to just use resolution with empty space rather than scaling it back up to the native then IQ should be fine

spacediver
Posts: 505
Joined: 18 Dec 2013, 23:51

Re: Does non-native Hz effect image quality?

Post by spacediver » 12 Aug 2015, 12:32

you're an absolute wealth of information and generosity, Falkentyne :)

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