Benq Instant mode IS flicker

Adjusting BENQ Blur Reduction and DyAc (Dynamic Acceleration) including Blur Busters Strobe Utility. Supports most BenQ/Zowie Z-Series monitors (XL2411, XL2420, XL2720, XL2735, XL2540, XL2546)
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4SR
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Joined: 17 Dec 2020, 21:08

Benq Instant mode IS flicker

Post by 4SR » 18 Dec 2020, 00:52

XL2411Z v4 (former v1)

TLDR: Instant mode is flicker. Result in most cases: mild to moderate eye dryness based on exposure duration.

This is 100% flicker, it does "dry" my eyes based on exposure duration. (Longer exposure -> drier eyes)
Dry is in quotes because im pretty sure (no solid proof however) that it just damages the very top layer of cornea and as you blink you get closer and closer to nerve ending that are underneath it. Good news: "Corneal epithelium - tissue layer of fast-growing and easily regenerated cells." ***Link that i cannot post to wiki /wiki/Cornea#Microanatomy ***
Some people hit harder. forums.blurbusters.com/viewtopic.php?f=2&t=2048&start=10

The next stop on this train is Recurrent corneal erosion (RCE). ***Link that i cannot post to wiki /wiki/Recurrent_corneal_erosion***
I got there with my left eye, by having PWM-flickering monitor to my left.(back in 2015)
I recovered from RCE by eliminating PWM, still exposed to Instant mode and all kind of LED bulbs flicker. My flicker testing method back then was the following. *** Google that video "Flicker-Free - BenQ VA LED Monitor GW2760HS" ***. Turns out it was limited to PWM type flicker only.

Jump to oct 2020 i discovered that setting exposure to some low value in camera settings is a better way to test for flicker. Luckily I was able to set exposure value in the "service menu" of my phones camera app.

This flicker is blur reduction method. There is massive improvement in motion clarity with flicker on.
This forum member explained everything [XL2430T]. forums.blurbusters.com/viewtopic.php?t=2750
You can only turn it off in certain Picture Modes (i used FPS1 to create my Gamer presets).
You cant turn it off in "Standard" Picture Mode AKA it is never flicker free.

Some LED light bulbs i tested produced similar flicker.

This is video of toggling Instant mode.
https://youtu.be/hDolW7OTMxo

This is more detailed video, however due to re-encoding there is so much artifacts that its hard to see the flicker.
Skip to around 2:00 for the stuff you can actually see.
https://youtu.be/YbzRyYQtYY4

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Chief Blur Buster
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Re: Benq Instant mode IS flicker

Post by Chief Blur Buster » 18 Dec 2020, 02:32

Interesting observations!

I wonder if this is increased flicker from stronger LCD inversion algorithm (lag-reducing) or coarser FRC algorithm (lag-reducing). Would be neat to see microscope macro (eBay lens attached to smartphone) high speed video of the subpixels in operation at a frame rate ~4x refresh rate to see what the cause of Instant Mode flicker is.

Does www.testufo.com/inversion or www.lagom.nl/lcd-test/inversion.php change color/appearance when Instant Mode is ON/OFF?

If not, might be FRC-related or backlight DC transients, e.g. Instant Mode robbing monitor processor cycles away from the PWM-free algorithm (e.g. microcontroller driven capacitor filtering of a DC backlight, creating PWM leakages in a PWM-free backlight).

So summary of three main possibilities:
- Flicker from changes to inversion algorithm
- Flicker from changes to FRC algorithm
- Flicker from DC transients in PWM-free backlight
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4SR
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Joined: 17 Dec 2020, 21:08

Re: Benq Instant mode IS flicker

Post by 4SR » 18 Dec 2020, 02:55

lagom test remain identical at all possible combos of [instant mode] X [blur reduction]

Moving Inversion Patterns changes alot.
BR ON + inst On = 1st bar is purple, 2nd is green, all 4 bars flicker alittle.
Best result persistence =3 Area =0.
Perst =3 Area = 40 first 2 bars turn into gradients [black to purple] and [black to green] respectivly.
Perst =3 Area around 63. All bars are mostly black and flicker alot.
BR off + inst ON = 1st and 2nd bar alternate
BR off + inst OFF = Free for all. 1st and 2nd bar alternate rly fast and all 4 bars flicker

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Re: Benq Instant mode IS flicker

Post by Chief Blur Buster » 18 Dec 2020, 12:13

It's probably very faint inversion-algorithm related flicker. Shallow-cycle flicker.

Ignore the alternating flicker; that is from TestUFO stutters and don't co-relate. What I'm interested in color changes (e.g. disappearance/appearance of non-greyscale colors)
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4SR
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Re: Benq Instant mode IS flicker

Post by 4SR » 18 Dec 2020, 17:10

****Forbidden. Message seems to be spam.****
Got some imgur pics for lagom test that i find interesting. Unrelated to anything below.

Moving checkboard
There is always 2x grayscale bars, and always 2x purple-green bars
[colored bar][colored bar][grayscale bar][grayscale bar]
[grayscale bar][grayscale bar][colored bar][colored bar]


IM ON
- When XL2411Z is primary [Ready state]. Well shit... my english skills are not up to this
Okay... So a "Cycle" will be bars moving from left to right [1200 pixels] @ 5 pixels per frame @ 144 fps = 720 pixels per sec

"Alternate" is bar changing color, i can see it being drawn top to bottom it leaves ghosting trail (like a scanline).
With BR ON [Persistence 3 Area 0] + IM ON. The drawing is separated by thin line (ghosting).

1st cycle: 1st bar green, 2nd bar purple
2nd cycle: 2nd bar purple, 1st bar green
3rd cycle: 1st bar green, 2nd bar purple [like 1st cycle]

around 10th cycle: I can see something is changed but cant quite understand yet.(bars start to ficker differently, they were still flickering in previous cycles)

around 20th cycle: bottom 20% of the colored bars starts to flicker with the oposite color
21st cylce : 1st bar [top 80% is green][20% bottom alternates between green and purple] 2nd bar is opposite
22nd cycle: 1st bar [top 75% is purple][25% bottom alternates between green and purple] 2nd bar is opposite


25nd cycle: 1st bar [top 50% is purple][50% bottom alternates between green and purple] 2nd bar is opposite


30 cycle: 1st bar [100% alternates between green and purple] 2nd similar

35th cycle is similar to 25th except its now top of the bars that do alternate and bottoms that are static

The whole thing is about 54 +-3 cycles long. Middle cycle (30th in above example) is most likely actualy 27th.
There is a tiny stretch (under 300 pixels) where everything is perfect and there is no flicker


IM OFF
2x Colored bars flicker between [purple][green][grayscale]. 2x grayscale bars.
- When XL2411Z is primary [Ready state]. Similar cycle transitions happen but they are dominated by 50-70% grayscale in the mix. (Aka bars are now 3 colored)

IM Toggle
The cycles continue through the toggle. I cant really tell what is happening during IM OFF, but going IM ON -> IM OFF -> IM ON it is clear to me that couple of cycles have passed.

4SR
Posts: 12
Joined: 17 Dec 2020, 21:08

Re: Benq Instant mode IS flicker

Post by 4SR » 18 Dec 2020, 20:41

For even screen Cycle length (e.g. 1200, 1202) the pattern goes like this
1st Cycle: [purple][green]
2nd Cycle: [green][purple]
3rd Cycle: [purple][green]

For odd length
1st Cycle: [purple][green]
2nd Cycle: [purple][green]
3rd Cycle: [purple][green]

Here is a vid (note first 3 cycles pattern doesnt change, as soon as i dragged the window the pattern switched)
youtu be 8CgaiLdmij8

Here is a long vid of odd length pattern, u can actually see what i was trying to describe
@ 0:35 it jumps from [purple][green] to [green][purple] early in the cycle for no apparent reason
@ 2:17 it jumps from [green][purple] to [purple][green] late in the cycle, but there is atleast a framedrop that follows
youtu be _aTyAXgcymA

4SR
Posts: 12
Joined: 17 Dec 2020, 21:08

Re: Benq Instant mode IS flicker

Post by 4SR » 20 Dec 2020, 01:14

It is probably backlight related as i have seen several LED bulbs that produce similar flicker.

60hz
Moving checkerboard test at 60hz IM OFF looks strickenly similar to 144hz IM ON
There is no visible flicker on camera with IM ON.
With same camera settings and BR ON, switching to IM ON doesnt move BR "flicker bars". (@ 3:15 2nd video in this thread for 144hz example)

120hz
There is no visible flicker on camera with IM ON.
BR "flicker bars" still dont move with IM ON.

125hz VT500
There IS visible flicker on camera with IM ON.
BR "flicker bars" still DO move with IM ON.

200hz
There IS visible flicker on camera with IM ON.
The "flicker lines" move noticeably faster

MagneticDev
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Joined: 16 May 2018, 06:36

Re: Benq Instant mode IS flicker

Post by MagneticDev » 04 Feb 2021, 08:48

And one interesting thing is, when you disable "instant mode" in srgb (on the xl2411z) and save the settings to user3, it enable low blue light mode. I've just noticed that.

4SR
Posts: 12
Joined: 17 Dec 2020, 21:08

Re: Benq Instant mode IS flicker

Post by 4SR » 11 Feb 2021, 17:10

Bit of false alarm on this one. It's just a bug.

IM[ON] is just a normal inversion flicker (lagom 4) (Line-paired RGB sub-pixel dot-inversion). Maybe exacerbated by my panels age.

IM[OFF] under FPS1 the panel operates in 120hz mode (frameskips, inversion at 60hz, BR at 120hz). Basicly broken.

It would be super nice if someone could explain why inversion flicker lines run slightly diagonally compared to Blur Reduction lines.
https://imgur.com/a/9iWwaXE

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