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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 k2viper » 05 Dec 2018, 01:59

Kheri,
I posted some pics of 120hz default (crosstalk) vs 120hz VT1580 and the difference was clearly seen. Crosstalk trails are definitely more faint. viewtopic.php?p=31012#p31012

Yes, at 240hz VT1304 is less visible improvement, but VT1580 120hz pics clearly shows that VT tweak is working as intended. Dont expect huge impressive change, because even at 120hz, it cannot reach high VTs like twice the frame height (2200 or so). It looks like firmware limitation of Mstar scaler device inside, because monitor at 240hz has a pixelclock headroom up to 640Mhz. I cant recall did I noticed the difference when going to VT1304. I'm on this mode from Feb 2018 and havent changed it. Theoretically larger VTs have benefits even if crosstalk dont visibly change, and as 120hz shows, VT tweaking is working as it should. So I'm on 1304 because its theoretically better.

You know, its like when you overclock the CPU, and then tweak some secondary things like memory timings or CPU cache speed. Theoretically it is an improvement, but then you start a game and struggle to catch the difference by a naked eye. I suppose VT1304 is just like this.

About shutter speed, there are custom camera apps for smartphones that can contorol shutter speed, though my pics of 240hz are taken by default budget Xiaomi Redmi 4.

I cant really say if your description of crosstalk you see is good or bad, we need pics good enough to judge about.

dogroll, currently there wasnt any differences reported between 3.06 and 3.07 firmware. Service menu also looks the same (no useful options found). I tried to google some decumentation on Mstar scaler device model mentioned in service menu, hoping to find VCPs (DDC/CI control commands) to have additional controls like Benqs have over the Area/Intensity of strobing, though no luck yet.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby Kheri » 05 Dec 2018, 06:45

k2viper wrote:Kheri,
I posted some pics of 120hz default (crosstalk) vs 120hz VT1580 and the difference was clearly seen. Crosstalk trails are definitely more faint. viewtopic.php?p=31012#p31012

Yes, at 240hz VT1304 is less visible improvement, but VT1580 120hz pics clearly shows that VT tweak is working as intended. Dont expect huge impressive change, because even at 120hz, it cannot reach high VTs like twice the frame height (2200 or so). It looks like firmware limitation of Mstar scaler device inside, because monitor at 240hz has a pixelclock headroom up to 640Mhz. I cant recall did I noticed the difference when going to VT1304. I'm on this mode from Feb 2018 and havent changed it. Theoretically larger VTs have benefits even if crosstalk dont visibly change, and as 120hz shows, VT tweaking is working as it should. So I'm on 1304 because its theoretically better.

You know, its like when you overclock the CPU, and then tweak some secondary things like memory timings or CPU cache speed. Theoretically it is an improvement, but then you start a game and struggle to catch the difference by a naked eye. I suppose VT1304 is just like this.

About shutter speed, there are custom camera apps for smartphones that can contorol shutter speed, though my pics of 240hz are taken by default budget Xiaomi Redmi 4.

I cant really say if your description of crosstalk you see is good or bad, we need pics good enough to judge about.

dogroll, currently there wasnt any differences reported between 3.06 and 3.07 firmware. Service menu also looks the same (no useful options found). I tried to google some decumentation on Mstar scaler device model mentioned in service menu, hoping to find VCPs (DDC/CI control commands) to have additional controls like Benqs have over the Area/Intensity of strobing, though no luck yet.


I was looking for 120hz pics in this thread but didn't have enough time to find them, so thank you for that. I can clearly see there's a difference between your pics. When I check 120hz on my screen there's no difference, but I will check one more time to be sure, as the pics kinda help show where any differences might be. I don't see why I wouldn't be able to recognize the difference IRL after checking 8 times, if I can tell the difference between your two pics (save for your pics being stationary images.)

I searched for camera apps and tried a couple out but didn't have any luck. I just have a tablet. Should I look again? Anyone have a suggested app?

"It looks like firmware limitation of Mstar scaler device inside, because monitor at 240hz has a pixelclock headroom up to 640Mhz."
-- You're saying the limitation isn't due to the pixelclock, correct? I remember checking the pixelclock and it was under 640Mhz and the monitor still blanking out.

"Dont expect huge impressive change, because even at 120hz, it cannot reach high VTs like twice the frame height (2200 or so)"
-- Yeah, that's unfortunate. The changes won't be much; I'd still like to see them, though. AFAICT, there's NO change on my monitor with different VTs, and I've checked at least a dozen times @ 240hz and quite a few times @ 120hz. We're using different versions though, yes? I understand you want / we need pics to really confirm anything or have anything objective, but to me it's pretty clear. I really need to find an app that'll increase shutter speed, or get a hold of a better camera/phone.

It'd be nice if LG would let us have the ability to change more things.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby Chief Blur Buster » 05 Dec 2018, 12:41

VT tricks can be extremely subtle in reducing strobe crosstalk.
This is what should happen with http://www.testufo.com/crosstalk animation test pattern while tweaking vertical totals.

Image
(Example for 120Hz blur reduction.... crosstalk patterns/spacings is often worse/different at 240Hz.... but it illustrates why we do Vertical Total tweaking, larger blanking intervals at the same Hz, always is better for motion blur reducing modes.)

Small increases in VT may only widen the clear zone by a few pixels taller.
Huge increases in VT are required to get very noticeable crosstalk zone thinnings.

(Yeah.... The art of "cramming LCD GtG into VBI" for strobe backlights.... made human-eye visible by TestUFO Crosstalk during strobe tuning.)
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby k2viper » 06 Dec 2018, 08:49

Thank you Chief, a perfect illustration of what to expect out of VT tweaking!

Kheri, yes I'm talking that ~1580 VT ceiling isnt due to pixelclock limits, since LG is capable of 640Mhz. It's probably a Mstar firmware limitation for 1080p, as this limit is the same for 120 and 144 and I tried 180hz.
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby Kheri » 06 Dec 2018, 10:07

The best I can manage are blurry/unfocused pics. Wish my camera would focus, it'd really help to have the pics, they just seem useless this blurry.
I went ahead and tried to look for even the minutest changes, and looked at the top and bottom of the screen.. maybe I haven't found the right area to check. But it's clear to me there probably isn't any change (at 120hz with different vtotals the change should be obvious - it's obvious in k2viper's pics.) So, is there any reason why there wouldn't be any change? Drivers? Software? GPU? Version? Etc. What could I do?

Yeah, noticed the limitation wasn't based on the pixelcock, as well. Too bad, I suppose. :/
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Re: LG 27GK750F-B - 240Hz, 27" 1ms Blur reduction, Freesync

Postby k2viper » 09 Dec 2018, 08:45

Another way you may try to kick VT tweak in, is Nvidia control panel custom resolution, if CRU doesnt work for you (btw make sure you start CRU with admin privileges).
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