VT trick problem

[Falkentyne]

IF you are not using blur reduction, do not use the VT tweaks at all.
The VT tweaks are ONLY used to 'trick' the monitor into running at a higher "dot clock" (MHz), at the same refresh rate. Since the dot clock is higher, the panel scanout of the pixel transitions is increased (since it's running faster), and this helps the panel refresh faster between strobe pulses. What this does is, it makes the crosstalk field size (basically, the boundary between the beginning and the end of the strobe pulse) smaller, or rather, it makes the size between the top crosstalk area and the bottom larger, so less of it is on the screen.

Lightboost mode does accelerated scanout by default, by a different LC panel update (extra hardware), and that automatically makes the crosstalk field almost nonexistent. Using vertical total tweaks attempts to force a faster scanout without using the extra hardware and per line overdrive features of lightboost mode, and while it does work ok, it doesn't quite match lightboost.

Ignoring the lack of per line overdrive, the only way to have the benq blur reduction scanout match lightboost's is to use a 0.167 or lower persistence, along with a 1502 vertical total. Then the crosstalk field will match lightboost perfectly (VERY VERY faint sign of a strobe pulse boundary at the top, none at the bottom), but the screen will be MUCH darker than lightboost mode.

Now sure, lightboost makes the ghosting and crosstalk much better overall, but you lose all brightness and color controls in lightboost mode, and the contrast color crush starts happening at 40 contrast instead of 50.

So yeah, VT tweaks are ONLY for benq blur reduction mode!

[tramas]

Ok, thanks the help.

Do you have any idea of why CRU is not working with my monitor?

[Falkentyne]

Could be the Nvidia drivers overwriting anything entered in CRU.
I don't have an Nvidia card; I only use my laptop with the Geforce 570m to watch videos, spectate games, play arcade emulators or initialize lightboost as a surrogate for my desktop monitors.

Both lightboost and using Vertical total tweaks (whether or not blur reduction is on or off) push the limits of the monitor and can degrade the image quality. You may notice, in lightboost mode, that you may seen alternating dark/light scanline effects that are not present even at 144 hz or 120hz. If you use a 1500 vertical total, even in NON Lightboost mode (e.g. no 1138-1149 VT's; these activate lightboost at 100 and 120hz) you will see the same type of lines, although not as intense as lightboost mode, because lightboost is accelerating the scanout, even more than the 1500 vertical total 'emulates' by raising the dot clock, even though lightboost doesn't increase the VT (except the VT totals which 'trigger' lightboost after the Nvidia drivers unlock the mode), the LC panel update timings push the panel even harder than a VT 1500 tweak does.

There is no drawback to using VT tweaks if you are using benq blur reduction, besides losing the ability to use the monitor "display mode" aspect scalings (as long as you stay under 3.0ms persistence at 120hz, the backlight LED's are within tolerances), except losing flexibility to make the top of the screen crosstalk free and having a higher brightness. At higher than a 1.0ms persistence (assuming VT 1500 tweak), the crosstalk field at the top extends down too far for my liking; 1.0ms is barely cutting it. 0.5ms makes the top crosstalk (strobe pulse) field almost completely off the screen but 0.5ms persistence is too dark for most FPS games, but makes the crosstalk border at the top look BETTER than lightboost does at 120hz (lightboost at 100hz is as clear at the top as strobe duty 001 (0.167ms persistence). Going lower than 0.5ms (requires the service menu; 002 and 001 strobe duty (0.167ms); the windows utility only goes down to 003) pushes the crosstalk completely off screen with strobe phase 000, but that's too dim to be usable.

If you wanted to match lightboost 10% @ 120hz (1.4ms persistence) in BBR mode, you would use a strobe duty of 009, but with the VT tweaks the crosstalk field would extend down the top 1/4 of the screen with no way to make the top clear again without going all the way to strobe phase 050+. Without VT tweaks at all, a strobe duty of 000 has the top of the screen crystal clear (besides the overdrive ghosting artifacts) with the bottom a crosstalk mess, and then you would adjust the strobe duty higher to try to improve the bottom, while sacrificing the top.

Fun fact:
In lightboost mode, with accelerated scanout and the LC panel timings, the TOP of the screen looks perfect while the bottom has inverse ghosting.

In Benq Blur reduction mode, the TOP of the screen has inverse ghosting while the bottom has 'regular' ghosting, and the ghosting is more intense than in lightboost mode (remember BBR doesn't have per line overdrive). At 0 contrast and lightboost mode, the ghosting from overdrive artifacts is almost nonexistent.

[masterotaku]

At 0 contrast and lightboost mode, the ghosting from overdrive artifacts is almost nonexistent.

Oh, that's a good trick. It also makes the LB -> BBR trick look much better (a lot less blue inverse ghosting).

Without VT tweaks at all, a strobe duty of 000 has the top of the screen crystal clear

I think you meant strobe phase there .

Somewhere in your post you said something about the crosstalk zone that is wrong in my opinion. In my experience, 000 strobe phase looks exactly like Lightboost (crosstalk position wise). A bit of crosstalk at the top (next frame starting to appear where the first UFO row is) and some ghosting at the bottom. A high strobe phase makes that next frame appear completely, making the top of the screen perfect while it leaves some crosstalk (more than the bit that was previously at the top) from the previous frame at the bottom. At higher Hz, crosstalk is harder to hide.

I prefer using the highest strobe phase I can get (before it starts reducing my strobe duty) because of that extra fame of less input lag.

[Falkentyne]

hmm..yeah...I did mean strobe phase.

I explained in an earlier post that Benq probably chose strobe phase 100 to attempt to make the top of the screen as identical to lightboost as possible (lightboost has the top of the screen pristine, with the bottom only showing some faint inverse ghosting, and no crosstalk), but at the expense of the bottom turning into a crosstalk mess. But lightboost has normal ghosting at the top of the screen (faint secondary trails which become almost completely invisible with a contrast of "0" on the 2720Z, and a contrast of 50 on the VG248QE) and inverse ghosting on the bottom of the screen. But since lightboost has accelerated scanout through the LC Panel updates, the blurry mess that you see down there (without VT tweaks) with strobe phase 100 in BBR mode is completely off screen and gone. Through the service menu, you can tweak the overdrive gain to make the -bottom- of the screen pristine (OD gain=0C instead of 0F), but that brings normal ghosting to the top of the screen as punishment.

In Benq blur reduction mode, you can improve the crosstalk to lightboost type levels with a 1500 Vertical Total, Strobe phase 000, and Strobe Duty 005 (0.875ms persistence)--this matches Lightboost 120hz crosstalk field (you can see the very top of the strobe pulse at 120hz lightboost, but there's no way to make that inverse and normal ghosting disappear, due to lack of lightboost's per-line overdrive.
Even if Benq had a firmware where you could adjust the overdrive gain (which we wish they DID), most likely, you would only wind up improving either the inverse ghosting OR the normal ghosting, while making one or the other worse.

I say that VT 1500, strobe phase 0 and strobe duty 005 match lightboost 120hz. But that's because 100hz lightboost is even clearer, pushing the strobe pulse boundary that you DO see in 120hz lightboost at the very top of the screen, completely OFF the screen--making it identical to strobe duty 001 (0.167ms persistence), but strobe duty 001 is extremely dark and just unusuable.

BTW someone said the lowest persistence is 0.167ms.
That's when using the 60hz backlight pulse widths (which are used by the panel when VT tweaks are active). If you are not using VT tweaks, 001 strobe duty has an even lower persistence. At 100hz, 001 stobe duty is 0.1ms persistence (!). At 144 hz, it's 0.07, less than half the brightness of our already too dim 0.167ms persistence!