Picture artifacts with VT1350 tweak on XL2720Z

[mdzapeer]

Anyone noticed a blinds type banding effect on certain colors when using the VT1350 tweak. It easier to see on blue/greyish colors.

[Q83Ia7ta]

Isn't VT tweak for XL2420Z? 24 and 27 panels differs...

[Chief Blur Buster]

Anyone noticed a blinds type banding effect on certain colors when using the VT1350 tweak. It easier to see on blue/greyish colors.

Short answer: This is normal as banding artifacts often shows up on all current 24" 1ms panels the higher the refresh rate you go (e.g. 144Hz). The VT1350 tweak accelerates the scanout, and creates the same effect.

Long answer: You're essentially doing 144Hz scanout speed during 120Hz, by accelerating the panel horizontal scanrate to a speed of (1350/1125ths) of the original horizontal scanrate. Do this test. Try 144Hz without the VT1350 tweak. You should see the banding effect appear.

120Hz with default VT (~VT1125)
= 1080 visible scanlines plus 45 blanking interval scanlines = Vertical Total 1125 = "VT1125"
= 1125 scanlines times 120 refresh cycles per second
= 1125 x 120 = 135000
= 135 kilohertz horizontal scan rate
= 135,000 scanlines per second
= each row of pixels takes 1/135000th of a second to paint on the LCD monitor.

Thusly, for comparision:
120Hz default VT1125 = 135000 horizontal scanrate = row of pixels scanned on LCD in 1/135000th of a second
144Hz default VT1098 = 158112 horizontal scanrate = row of pixels scanned on LCD in 1/158112th of a second
120Hz tweaked VT1350 = 162000 horizontal scanrate = row of pixels scanned on LCD in 1/162000th of a second

So you see, 120Hz with tweaked VT1350 has a similar scanrate as 144Hz at default VT (which is VT1098 by Windows default, a reduced blanking interval).

"scanned", meaning voltage being injected into the pixels to start the pixel momentum (grey to grey). Pixels keeps coasting to its final color value long after the scanning voltage has been injected into the pixels. Less time for injecting voltage into pixel, means more color inaccuracies. That is why color degrades at higher refresh rates, and/or scanline artifacts show up (e.g. imbalanced pixel inversion). It is also why there can be very slight color degradation when adding the VT tweaks. The faster scanrate has the advantage (on the Z-Series) of a longer blanking interval, which means more time for the pixels to settle (finish GtG) between refreshes, for good strobe-backlight operation (strobing on fully refreshed, clear frames, minimizing strobe crosstalk).

[mdzapeer]

Thanks for explanation chief.

I guess I will keep the VT1350 for lower refresh rates. Rough calculation puts it at 100 hz max before artifacts become visible again.

[Chief Blur Buster]

Keep in mind that smaller the VT, the worse the strobe crosstalk (double image effect) becomes during motion blur reduction (strobe backlight operation).

[alex667]

Which VT tweak should I take with xl2411z @144 hz in csgo ?

[Q83Ia7ta]

Which VT tweak should I take with xl2411z @144 hz in csgo ?

There are no VT tweaks available for 144hz afaik