Backlight bleed?

Ask about motion blur reduction in gaming monitors. Includes ULMB (Ultra Low Motion Blur), NVIDIA LightBoost, ASUS ELMB, BenQ/Zowie DyAc, Turbo240, ToastyX Strobelight, etc.
Post Reply
thetwistedblue
Posts: 7
Joined: 15 Jan 2014, 12:54

Backlight bleed?

Post by thetwistedblue » 15 Jan 2014, 15:11

Hi guys,

I've only recently discovered the joys of Lightboost! However, I'm having two issues when using Lightboost with my Benq XL2411T at 120Hz (with AMD 7870 XT).

Firstly, I seem to be getting backlight bleed. I've borrowed a picture from overclockers.co.uk to show you what it looks like;
Image
I get these bands of brightness going across the screen with blotches in the middle, almost identical to the picture above.

Secondly, I seem to have an awful lot of scan line area, in the top right of my screen and down part of the left hand side. Scan lines being the faint horizontal lines. This picture is borrowed from overclock.net to show you what I mean;
Image

Is anyone aware of anyway to reduce these issues? My monitor was bought from Amazon back in May 13, so I'm not sure I could return it even if I wanted to..

User avatar
Chief Blur Buster
Site Admin
Posts: 11648
Joined: 05 Dec 2013, 15:44
Location: Toronto / Hamilton, Ontario, Canada
Contact:

Re: Backlight bleed?

Post by Chief Blur Buster » 15 Jan 2014, 15:23

thetwistedblue wrote:I've only recently discovered the joys of Lightboost! However, I'm having two issues when using Lightboost with my Benq XL2411T at 120Hz (with AMD 7870 XT).
Welcome to the wonderful world of motion blur eliminating strobe backlights. :D
I bet you've already experienced turning ON/OFF LightBoost during http://www.testufo.com/photo and seen the remarkable ability of an LCD to have perfectly clear fast motion, just like a CRT.
thetwistedblue wrote:Firstly, I seem to be getting backlight bleed.
Short answer:
This isn't backlight bleed, but actually a normal artifact of LightBoost. LightBoost pushes the limitations of LCD more aggressively, which creates some amplified "backlight-bleed-style" artifacts similar to these.

Long, complex, geeky answer:
This is normal on LightBoost, and is either a symptom of different pixel freshnesses before the backlight strobe flash, and/or the Y-axis-compensated response time acceleration. Some additional information is found at:
http://www.blurbusters.com/faq/creating ... #overdrive
http://display-corner.epfl.ch/index.php/LightBoost
What this means is that the LCD black levels may biased differently depending on the vertical dimension, because of the age of the pixel refresh relative to strobe flash -- LCD displays are refreshed in a top-to-bottom manner (see high speed videos), and that means there's less time for pixels to finish refreshing at the bottom of the screen before the strobe backlight flash occurs (LightBoost strobing). You also need more aggressive overdrive at the bottom edge of the screen than the top edge of the screen. This inevitably creates bands of different artifacts. Which may also be affecting things during blacks, too. It is also visible in full-screen Flicker Tests (http://www.testufo.com/flicker with Height -> Full Screen) which is another way to show the physical evidence of Y-axis-compensated overdrive algorithm that's in use within a LightBoost monitor.
thetwistedblue wrote:Secondly, I seem to have an awful lot of scan line area, in the top right of my screen and down part of the left hand side. Scan lines being the faint horizontal lines.
Short Answer:
This is another normal artifact of many LightBoost monitors, but this one actually varies a lot from monitor to monitor. Newer LightBoost monitors, manage to eliminate this artifact (e.g. I've almost never seen anyone report this problem with BENQ XL2420TE).

Long Answer:
This is actually an interaction between strobing and LCD inversion (a temporal method of LCD panels to keep DC voltages balanced), that ends up creating this pattern. For more information about the purpose of LCD inversion in keeping a panel electrically balanced, see http://www.testufo.com/inversion and follow the links at the top (Lagom and Techmind) for the scientific explanations. The motion test itself will look quite weird (purples and greens will show up; this is normal and happens on almost all LCDs using the common tall-checkerboard inversion pattern.). There is a panel lottery factor that increases/decreases the intensity of this otherwise common LightBoost artifact. If this artifact bothers you, you may wish to upgrade to a newer monitor later this year.

Newer strobe backlights are improving, and panels are improving. LightBoost was the first strobe backlight that really did a super-good job of reproducing CRT motion clarity on an LCD desktop monitor, and is quite bleeding edge; it pushes the limitations of many LCD panels.
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

Image
Forum Rules wrote:  1. Rule #1: Be Nice. This is published forum rule #1. Even To Newbies & People You Disagree With!
  2. Please report rule violations If you see a post that violates forum rules, then report the post.
  3. ALWAYS respect indie testers here. See how indies are bootstrapping Blur Busters research!

thetwistedblue
Posts: 7
Joined: 15 Jan 2014, 12:54

Re: Backlight bleed?

Post by thetwistedblue » 15 Jan 2014, 15:30

Chief Blur Buster wrote:Welcome to the wonderful world of motion blur eliminating strobe backlights. :D
Hi! Thanks for your fantastically quick and complete response to my questions!
Chief Blur Buster wrote:I bet you've already experienced turning ON/OFF LightBoost during http://www.testufo.com/photo and seen the remarkable ability of an LCD to have perfectly clear fast motion, just like a CRT.
This absolutely blew my mind when I first tried it, I've been showing my girlfriend repeatedly for the past 2 days. She's so sick of seeing that picture! :D

Literally, she gets motion sickness. :shock:

But yes, aside from that, thanks again for such a detailed response, you've put my mind at ease.

User avatar
Chief Blur Buster
Site Admin
Posts: 11648
Joined: 05 Dec 2013, 15:44
Location: Toronto / Hamilton, Ontario, Canada
Contact:

Re: Backlight bleed?

Post by Chief Blur Buster » 15 Jan 2014, 16:24

All strobe backlights can sometimes add tradeoffs. But if you are seeking a model with fewer tradeoffs, there are better ones coming out as time passes.

I presume you have already played with different LightBoost levels (e.g. LightBoost=10% through LightBoost=100%), as LightBoost monitors are adjustable-persistence monitors.

If you can't wait today, I highly recommend the Eizo FG2421 monitor. EIZO's equivalent of LightBoost strobing, is Turbo240. Its motion clarity is only equivalent to LightBoost=70% but you get much brighter image, better blacks, VA colors, which might be more pleasing to your eyes. The panel does need a warmup time (30 mins) for minimum ghosting, and it does have slightly higher input lag on this model (19ms) but this is still less than many 60Hz monitors. It is a very good panel if you want the best colors/blacks in a strobe backlight that money can buy today, if you are willing to live with other tradeoffs!
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

Image
Forum Rules wrote:  1. Rule #1: Be Nice. This is published forum rule #1. Even To Newbies & People You Disagree With!
  2. Please report rule violations If you see a post that violates forum rules, then report the post.
  3. ALWAYS respect indie testers here. See how indies are bootstrapping Blur Busters research!

User avatar
RealNC
Site Admin
Posts: 3741
Joined: 24 Dec 2013, 18:32
Contact:

Re: Backlight bleed?

Post by RealNC » 15 Jan 2014, 19:05

Personally, I cannot make out any blur on that moving picture (I don't have an LB monitor, just plain old 60Hz.) Maybe I should go check my eyes :-P
SteamGitHubStack Overflow
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.

User avatar
Chief Blur Buster
Site Admin
Posts: 11648
Joined: 05 Dec 2013, 15:44
Location: Toronto / Hamilton, Ontario, Canada
Contact:

Re: Backlight bleed?

Post by Chief Blur Buster » 15 Jan 2014, 21:20

RealNC wrote:Personally, I cannot make out any blur on that moving picture (I don't have an LB monitor, just plain old 60Hz.) Maybe I should go check my eyes :-P
You're not looking closely enough. ;)
Check this one out: TestUFO Panning Map Test

You can only read street name labels on this panning map successfully on a CRT or a strobe-backlight LCD:


The full screen version is here, maximize your browser. Try to read the map labels at 1440 pixels/second. Can you?
On LightBoost or ULMB, the map is as sharp as a paper map moving sideways, and you can easily read the map labels.

IMPORTANT: See system requirements for a stutter free web browser experience for TestUFO motion tests, running at a frame rate successfully synchronized to refresh rate (e.g. Chrome, running on Windows systems, in Aero mode NOT classic, on the Primary monitor, with a green "VALID" displayed at the bottom)
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

Image
Forum Rules wrote:  1. Rule #1: Be Nice. This is published forum rule #1. Even To Newbies & People You Disagree With!
  2. Please report rule violations If you see a post that violates forum rules, then report the post.
  3. ALWAYS respect indie testers here. See how indies are bootstrapping Blur Busters research!

Post Reply