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I was wondering about the following. Now that g sync allows a variable refresh rate does that mean it would be possible to implement during lighthboost strobe so to make black frame insertion shorter?

Basically since we don't care about the black frame since we cant see it, why render it? Just shut down the LED shortly (1/4 or 1/2 a frame) before displaying the next frame. it seems like a waste of processing power to render frames we don't see. That way a 120 hz monitor could still display 90 lighted frame since the 90 black ones require the same time as 30 frame?

Or maybe that wouldnt work, i'd like some more technological input on the limitations of this idea. I don't say that g-sync and lighboots strobe should be combined, but that both those technology (strobe and variable frame refresh of a monitor) made me think about this idea.

Hope i was clear enough as when i'm thinking of this i'm rather confused myself lol

SS4 wrote:I was wondering about the following. Now that g sync allows a variable refresh rate does that mean it would be possible to implement during lighthboost strobe so to make black frame insertion shorter?

Basically since we don't care about the black frame since we cant see it, why render it?

Black frame insertion does not cause extra frames to be rendered. Frames aren't "wasted" during black frame insertion. There is a TestUFO software-based black frame insertion animation, which is embedded below:



So both are same frame rates, except the black frame eliminates a repeat copy of the frame. So no extra frame rate or rendering rate is needed during black frame insertion, it simply shortens the persistence of each static frame, by halving the amount of time a static frame is displayed. This reduces eye-tracking based motion blur (another animation).

IMPORTANT: For accurate animation reliability (no erratic flickers), view the above animation in a stutter-free web browser, Aero enabled, Classic mode disabled, GPU acceleration enabled, desktop computer rather than mobile browser, all windows on primary monitor, other apps closed, to ensure that the above animation doesn't "flicker erratically".

Although usually black frame insertion is traditionally a blank black frame between frames, it doesn't necessarily have to be that way. Sometimes it's a brief frame (shown shorter than the visible frames) and sometimes it's a long frame (shown longer than the visible frames). Black frame insertion can either be done via the refresh or via the backlight. LightBoost is sort of like black frame insertion, what matters is blackness between refreshes to shorten the persistence of the visible refreshes. Another example animation that demonstrates how different duty cycles of blackness (during black frame insertion) affects motion blur: Black Frame Insertion of Different Duty Cycles

SS4 wrote:Just shut down the LED shortly (1/4 or 1/2 a frame) before displaying the next frame. it seems like a waste of processing power to render frames we don't see.

That's what LightBoost already essentially does, except at a fixed strobe rate. (and others such as Turbo240/BENQ Z-series). As seen in high speed video.

SS4 wrote:That way a 120 hz monitor could still display 90 lighted frame since the 90 black ones require the same time as 30 frame?

Unfortunately, variable strobe rate is an engineering problem that is difficult. If you had a random flicker, it would be annoying to human eyes. Also see other sites; Toms Hardware saying variable strobe rate is an engineering issue.

SS4 wrote:Or maybe that wouldnt work, i'd like some more technological input on the limitations of this idea. I don't say that g-sync and lighboots strobe should be combined, but that both those technology (strobe and variable frame refresh of a monitor) made me think about this idea.

I've already written about this idea in as a section of my document, Electronics Hacking: Creating A Strobe Backlight. Several manufacturers have read that document already, which is my findings based on my Arduino Scanning Backlight experiments that started off Blur Busters.

Hope i was clear enough as when i'm thinking of this i'm rather confused myself lol

Hope my reply at least clarified a few things.
Feel free to ask questions... No question is too silly to ask on Blur Busters Forums -- we're all about spreading the word about improving motion quality on monitors!

If frames arent wasted during black frame insertion wiht lightboost, why do we need 120 + FPS for best result? It only renders 60 real frames ? is it because the timing is different which means 61 all the way to 119 wouldnt match so it needs exactly 60 as everything over unless its over 120 makes it wrong? If so g sync combine with lightboost would work under 120 FPS (and hopefully we can use lightboost at 144hz soon).

As for the shorter or variable flicker i was just hoping there was a way to either increase FPS or brightness in such a way during lightboost.

I did suspect there was a technical barrier but I just wanted to get detailed info on this aspect from someone who knows what hes talking about

SS4 wrote:If frames arent wasted during black frame insertion wiht lightboost, why do we need 120 + FPS for best result?

That's because it's 120 true frames per second.

SS4 wrote:It only renders 60 real frames ?

No. It's a fixed strobe rate.
e.g. 120 flashes per second at 120Hz

SS4 wrote:Is it because the timing is is different which means 61 all the way to 119 wouldnt match so it needs exactly 60 as everything over unless its over 120 makes it wrong?

No, it doesn't work that way.
LightBoost, being a hardware method of black frames, preserves the full refresh rate.
The visibility of each refresh is simply shortened by flashing each refresh with the strobe backlight.
So it's adding black frame insertion without throwing away refreshes.

120fps means each frame is normally 1/120sec long (Mathmeatically 1/120 = 8.3333). So that's 8.3 milliseconds.
LightBoost simply flashes for around 1ms to 2.5ms, and is dark the rest of the time. For example, out of 1/120sec, 1.4ms flash (visible frame) followed by 6.9ms of off backlight (black frame effect).

So LightBoost preserves the refresh rate. It just makes each refresh shorter, in order to insert blackness between each refresh at the existing refresh rate.

By default, LightBoost (configured to 100%) strobesusing 2.4 millisecond flashes. However, it can be shortend to around ~1ms-1.5ms for LightBoost=10% setting (varies between different models of LightBoost monitors). Since 1.4ms is 1/700sec, metaphorically it is like 700 frames per second where only 120 frames are visible and the rest are black frames. We don't normally call LightBoost "black frame insertion", since it's a backlight driven method, but if it were described as a hardware backlight-based black frame insertion, it can be pictured that way. (It's actually true we'll need a flickerfree/strobefree 700fps@700Hz monitor in order to match LightBoost motion clarity -- this would be a very difficult engineering challenge).

See high speed video of LightBoost:
This is simply a high-speed video of www.testufo.com/flicker (in full-screen mode)



Now, LightBoost is intentionally currently limited to strobing at 100Hz through 120Hz, because that's a vendor decision (NVIDIA) to limit the strobing to a range of 100Hz through 120Hz, much like a CRT that's limited to 100Hz to 120Hz. And since you need framerate=stroberate for best motion clarity (e.g. 120fps@120Hz), that's why LightBoost requires a lot of GPU to look really good. Strobe backlights aren't technologically limited to these strobe rates, as the upcoming BENQ XL2720Z supports strobing as low as 75Hz (vendors are reluctant to allow 60Hz strobing because it would flicker annoyingly -- like an old-fashioned 60Hz CRT).

Some related reading:
- PHOTOS: 60Hz vs 120Hz vs LightBoost
- PHOTOS: LightBoost 10% vs 50% vs 100%

And a very useful comparison image:

(Mathematically, 1ms of persistence = 1 pixel of tracking-based motion blur during 1000 pixels/second)

Ok, its clear now. i think what confused me is the UFO test on the website which works on regular monitors that misled me to believe lightboost behaved in the same way. But thx for clearing up that confusion. i knew i was misunderstanding something lol

SS4 wrote:Ok, its clear now. i think what confused me is the UFO test on the website which works on regular monitors that misled me to believe lightboost behaved in the same way. But thx for clearing up that confusion. i knew i was misunderstanding something lol

Software-based black frame insertion, by necessity, has to run at a frame rate lower than the refresh rate.
Hardware-based black frame insertion (especially backlight-based) has no such limitation.

I'll edit the TestUFO test to make that clear. Wording suggestions are always welcome, to reduce confusion.

Well, i now see that the lightboost mod and black frame insertion have different execution and are not the same although they accomplish the same thing. Lightboost makes the LED go On and Off during a single frame so your frame rate stays the same. While black frame insertion just use half your frame rate to display a black screen and the other half to display the actual content giving you the same motion clarity effect without the hardware restriction although your visible FPS are cut in half.
In a way lightboost is almost like doubling your frame rate if you count the LED off state as a refresh cycle.

Hey Mark, great work on the site and all your explanations. I'm still trying to wrap my head around this.

So, say I buy a typical 120hz monitor and I can only get 60 frames in a game.
I assume the monitor still refreshes at 120hz and will simply show the same frame twice like my current 60hz monitor does when I get 30fps.

If this is the case, why wouldn't lightboost help with the motion blur with 60 "real" fps in some particularly demanding game? Why wouldn't it just always strobe at the 120hz? If it strobes the backlight at 120hz, even if it strobes it twice per actual new frame, it should still help eliminate the persistance, no?

Well since you are showing the same picture twice then there is persistence imo. Like looking at a slide show, no matter if it flashes or not its still a slide show right . . .

But there would be less motion blur between the old and new frames, so it would still be far better than a typical 60hz motion blurry monitor, even if the framerate stays the same, right?