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LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby dogroll » 17 Feb 2018, 06:18

Nope, I did not find that feature.

I have to say that I think the strobe crosstalk at 120 and 144Hz is not so bad. And I've mainly been using it at 240Hz without strobing, as the sample and holds motion blur there is low enough that I don't think I need the strobing.

What gamma mode did you set? I found mode 4 to look the most normal (close to 2.2) before calibration.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby k2viper » 17 Feb 2018, 08:02

dogroll wrote:What gamma mode did you set? I found mode 4 to look the most normal (close to 2.2) before calibration.


Uhm, default I think (mode 2), havent tweaked gamma nor black stabilizer from defaults. I dont have a colorimeter and felt that colors/gamma/contrast was pretty fine at defaults.
All I did is lowering brightness to 50 (i'm playing and using monitor in dark conditions, default brightness is too high), also I'm sticked with blur reduction at 240hz.

dogroll wrote:I have to say that I think the strobe crosstalk at 120 and 144Hz is not so bad. And I've mainly been using it at 240Hz without strobing, as the sample and holds motion blur there is low enough that I don't think I need the strobing.


120hz crosstalk is bad comparing to my old Asus VG278H (lightboost). And I also found that its 240hz non-strobed mode is absolutely usable, there's some my pics of it on page 5. I'm just used to MBR, thats why I'm still using it, but I also confirm, 240hz nonstrobed is absolutely usable and has pretty low motion blur.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby dogroll » 17 Feb 2018, 22:01

I'm not terribly familiar with how to set up custom resolutions. How do I go about reducing crosstalk at 120hz? I made a new 120hz 'detailed resolution' with much larger vertical total, then restarted PC, but I saw no difference in the crosstalk test on testufo.com. I didn't see a new 120hz resolution in the windows resolution list -- are the changes made by CRU supposed to be baked into the already existing 120hz option after a restart, or did it not work?
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby k2viper » 18 Feb 2018, 11:05

Try nvidia control panel, there is "test" button and you can immediately try, is the new res working. Max VT I found for 120hz was between 1580 and 1600 (same max VT for 144hz, at higher VT strobing goes off).
If high VT works, crosstalk should be reduced, but yes, at 120hz its just bad.

120hz strobed is basically worst out of 3 modes this monitor provides.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby dogroll » 18 Feb 2018, 17:06

k2viper wrote:Try nvidia control panel, there is "test" button and you can immediately try, is the new res working. Max VT I found for 120hz was between 1580 and 1600 (same max VT for 144hz, at higher VT strobing goes off).
If high VT works, crosstalk should be reduced, but yes, at 120hz its just bad.

120hz strobed is basically worst out of 3 modes this monitor provides.


Have AMD card :^) it is a freesync monitor after all. I tried creating custom resolution through the AMD driver but had the same problem, and there's no test button.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby k2viper » 19 Feb 2018, 01:53

Well, 120hz strobed is just "bad" on this monitor, it does not mean VT tweak not working.
I think strobe length is just excessively high at 120hz, it strobes longer then display scans out a frame, that's why we cannot avoid crosstalk completely, even kicking in high VT. If there will be any way to control strobe length (service menu, DDC/CI etc), monitor would be a gem.

120hz default
Image

120hz VT 1580. Not much of a difference, but it can be seen if you look closely, center looks clearer. So, I think VT tweak working as intended.

ImageImage
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby Chief Blur Buster » 19 Feb 2018, 12:53

But have you tried even bigger vertical totals?

With 120Hz on a 240Hz monitor you should be able to support double size vertical total as 240Hz. So you should theoretically support VT2652 (double your VT1326) -- or VT2604 120Hz for a VT1302 240Hz -- essentially an exact double VT for half refresh rate. (assuming Horizontal Total is the same for both modes). Exact same Pixel Clock means you can exactly double your Vertical Total while halving your refresh rate (while maintaining same Horizontal Total). Or quadruple Vertical Total for one-quarter refresh rate.

To attempt a largest possible vertical total, follow Appendix A of blurbusters.com/crosstalk

Basically, get your biggest VT 240Hz you successfully done as Step #2 of Appendix A.

That's how you achieve VT's well into the 2000+ range during 120Hz for a 240Hz strobed monitor.

(FWIW, the biggest VT I've ever seen is approximately ~VT4500 at 60Hz on a 240Hz monitor.). When VT padding is via Vertical Front Porch, this is a "Quick Frame Transport" (QFT, like HDMI 2.1) refresh-cycle-delivery speedup factor of 4x for VSYNC ON gameplay, by the way -- reducing VSYNC ON lag of 60Hz by 3/4ths of a frame! Does not affect VSYNC OFF input lag, though.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction

Postby A Solid lad » 19 Feb 2018, 19:05

k2viper wrote:I took some pictures, but I think you dont want to look at standard package and display body pics, but crosstalk shots I took look very smeared, I need to try different camera or camera settings.

You thought wrong!
I would like to look at those photos! :D
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Monitors I've used/use: IBM p275, Benq XL2411Z, Alienware AW2518Hf, Alienware AW2518H, Acer XF270HA, LG 27GK750F-B, Benq XL2740, ACER XB271HU, ACER XG270HUa, Benq XL2720Z, Benq XL2540
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby A Solid lad » 19 Feb 2018, 19:56

Just read a bunch more about the monitor and came across some oddities.

Image

First things first, what's up with the word "faster" in brackets?
And then... what is 1ms motion blur reduction supposed to mean? 1ms persistence?
or 1ms response time...but only when strobed? that wouldn't make much sense...

and to top it all off, they also state on the product page, that blur reduction can't be used together with Fresync and "DAS" with the latter being a complete mistery box, even after googling around...
The only information I could find about "DAS" is that it's supposed to reduce input lag... (similarly to Benq's instant mode, I assume, but don't quote me on that)
However, not being able to use instant mode when strobing, wouldn't make much sense either, now would it?
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby Falkentyne » 19 Feb 2018, 23:11

k2viper wrote:Well, 120hz strobed is just "bad" on this monitor, it does not mean VT tweak not working.
I think strobe length is just excessively high at 120hz, it strobes longer then display scans out a frame, that's why we cannot avoid crosstalk completely, even kicking in high VT. If there will be any way to control strobe length (service menu, DDC/CI etc), monitor would be a gem.

120hz default
Image

120hz VT 1580. Not much of a difference, but it can be seen if you look closely, center looks clearer. So, I think VT tweak working as intended.

ImageImage




Just looked at your pictures.
I think you're being WAY too harsh on your monitor.
The crosstalk at 120hz default is *MILES* better than any of the Benq monitors at 120hz without a VT tweak.
At VT 1580, your crosstalk is slightly better than a 120hz Benq XL monitor with VT 1500 active, using a "high" strobe phase to make crosstalk at the top of the screen equal to zero (exact settings: Strobe Phase =044, Strobe Duty=006, 1.0ms screen strobe persistence).

Yes, we all want absolutely no crosstalk, but to do that on a 27" monitor, would require a MUCH higher VT. Can you go higher than VT 1580?

The Benq XL2735 was tested by CallsignVega (Vega on these forums), to run at 120hz with a VT of 1825, if I recall correctly The default VT for this monitor at 2560x1440 @ 120hz was VT 1525.
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