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XL2546 vs. XL2540? Which should I get?

Discuss BENQ Blur Reduction (strobe backlight) and the Blur Busters Strobe Utility. For Z-Series monitors (V2 firmware) on XL2411Z, XL2420Z and XL2720Z.

Re: XL2546 vs. XL2540? Which should I get?

Postby Falkentyne » 02 Sep 2017, 18:22

Yes it is.
The main question I've been wondering very intensely is this.

As you know, the XL2540 supports Freesync (adaptive Sync), but this only works if Blur Reduction is disabled in its service menu. The monitor ships with its blur reduction disabled by default. That's why originally people thought this was a 240hz panel without blur reduction, until someone found the setting in the service menu. Benq nowhere even marketed this monitor as supporting blur reduction.

The XL2546 functions like the XL2735..."DyAc" is Benq blur reduction renamed and marketed, and is set to ON by default. This also means freesync/adaptive sync won't work. The big question I asked is, if you disable DyAc (blur reduction), will freesync work again on AMD cards on the XL2546?

If it does, then will it also work on the XL2735?
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Re: XL2546 vs. XL2540? Which should I get?

Postby BurzumStride » 08 Sep 2017, 09:59

Hey, great work guys thanks so much for all the information. These forums are my absolute go-to for everything display-related, and I finally got around to making an account! This post may have just saved me a lot of money.

I am in the same boat as the op. However from what I am reading here, I find it hard to justify an extra £100 for the XL2546, solely on an increased strobed brightness and *potentially* improved strobing performance.
Would anyone who has used the XL2540 be able to tell me if the monitor is bright "enough" with the maximum phase/area setting at 240hz?

I'm talking here about daylight blinds-shut/night sessions of BF4 with Nvidia's digital vibrance maxed out (+ any other colour-bleed inducing/non-input-lag causing technologies I'll be able to get my hands on).

Also, am I correct in understanding that the Benq Blur Reduction adds 0 frames of delay at the maximum phase/area setting?
I recall reading Falkentyne's post, stating that the utility-tested "1 frame delay" value was incorrect.
The competitively non-intrusive blur reduction is my main reason for choosing this monitor over the upcoming 240hz ROG Strix (freesync).

//Is this an appropriate way to post, or did I just semi-hijack someone else's thread?
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Re: XL2546 vs. XL2540? Which should I get?

Postby Chief Blur Buster » 08 Sep 2017, 23:08

Simple answer: Strobing adds an average of half a refresh cycle input lag (all pixels, averaged).

Long answer: Exact answer is far more complex than that.

For all locations of screen, average lag stays constant, but changing strobe phase will decrease lag for one part of screen and increase for a different part of screen. When we're adjusting strobe crosstalk, there's a band of double-images that moves up/down during strobe phase adjustments. Above the "strobe crosstalk band" has the least lag and below the "strobe crosstalk band" has the most lag. Going from 0 to 100 wraps around so 0 and 100 has identical lag. As the strobe crosstalk band moves up/down, the lag-gradient follows with it.

Remember, that top, center, and bottom have different lag results. All strobe phases (when combined with VSYNC OFF) tends to average out to the same lag. The big question is whether you want the least lag for top edge, for center, or bottom edge. The strobe phase affects that.

Also, the "frames of lag" thinking doesn't take into account of factors like lag gradients (between top/bottom edges of frame slices between tearlines during VSYNC OFF) and scanout lag (where top/center/bottom of screen diverges, more noticeable during VSYNC ON). Consider that strobing is a hidden-scanout-delay-then-sudden-global-visibility, and non-strobing is sequential scanout. There are complex lag interactions between scanout-lag, between the tearslices lag graidents, and between the global strobing.

--> If you want least lag for screen centre, adjust strobe phase until the crosstalk band is right below the screen centre. Lag is lowest immediately above the crosstalk band and lag is highest below the crosstalk band.

The bottom line is: Properly Using ULMB Beautifully or Competitively -- where human reaction times for certain game tactics can greatly outweigh strobe lag.
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