- May 5, 2006
I'm not a fan of BFI in it's current forms with current display limitations. It's essentially PWM, and it dims/mutes color vibrancy. That means detail-in-colors can be lost and color brilliance muted. Therefore BFI obviously doesn't work with HDR color brightness and hdr ranges of detail-in-colors - which are already restricted on OLED in order to avoid burn-in. Additionally, reviewers say high BFI on the CX is noticeably flickery. The other levels are still flickering even if you can't really notice it consciously though, like PWM. That causes eye fatigue and even eye strain.The best setting for this display if you have the horsepower will be: 4K - 120Hz - BFI "high" - FPS cap set to 119.993 via RTSS - VSync set to "On" in-game.
That way you don't get the V-Sync - ON input lag, and the FPS is so closely synced still for BFI that the occasional single micro-stutter is minutes apart and not noticeable, and you have no screen tearing. 4.16ms MPRT motion clarity.
To me it seems like the tradeoffs for medium BFI are way too much for too little. For high the flickering rules it out entirely. For low the effect is way too little compared to just running high frame rates to reduce sample and hold blur so I wouldn't even bother taking any tradeoffs for that. Anyway, in it's current limitations BFI is not for me personally.
That said, I did look up some info about it back when it was being heavily discussed in this thread and found details about how much different the oled rolling scan BFI is from what most people are familiar with in LCD backlight strobing so I thought I'd post that reply again here with the relevant quotes.
I wanted to know the details of how it works as well, especially with VRR activated and working fully because your frame rate and hz would be varying and for most people dropping considerably on the low end of a game's graph. A 60-90 -130 graph didn't seem like it would play nice with bfi.Does BFI work with any refresh rate? Like, 75hz, 90hz, 101hz, etc? Or do you have to choose either 60 or 120hz?
It seems like "chief blurbuster" mark r is saying the hz/fps is unlinked from the black frame since its a per pixel strobe.
"Hz and persistence can be unlinked/unrelated thanks to strobe duty cycle adjustment."
"Does not matter if full strobe or rolling scan, as it is per-pixel duty cycle.
Note: That said, non-global illumination can cause artifacts (e.g. skewing during scan of any CRT, OLED (including strobed and nonstrobed rolling scans) or nonstrobed LCD"
"rolling strobe on OLED can be fractional refreshes, so OLED BFI can actually be arbitrary lengths unrelated to refresh cycle length. Since the off-pass can chase behind the on-pass simultaneously on the same screen at an arbitrary distance"
from blurbusters. com
Strobing on OLEDs sometimes have to behave differently because there’s no independent light source separate from pixel refresh source like for LCDs.
As a result, strobing on most OLEDs are almost always rolling-scan strobe (some exceptions apply, as some panels are designed differently OLED transistors can be preconfigured in scanout refresh, and then a illumination voltage does a global illumination at the end).
However, most large OLED panels have to do a rolling-scan strobe for reducing persistence. Also, rolling strobe on OLED can be fractional refreshes, so OLED BFI can actually be arbitrary lengths unrelated to refresh cycle length. Since the off-pass can chase behind the on-pass simultaneously on the same screen at an arbitrary distance, much like it did on the Dell UP3017Q monitor. Like changing the phosphor of a CRT to a shorter or medium persistence (except it’s a squarewave rather than a fade wave), CRT phosphor persistence length being unrelated to refresh cycle length. So BFI isn’t necessarily integer divisors here, and the meaning of “strobing” vs “BFI” is blurred into one meaning.
- An OLED with a 50%:50% on BFI will reduce motion blur by 50% (half original motion blur)
- An OLED with a 25%:75% on BFI will reduce motion blur by 75% (quarter original motion blur)
Typically, most OLED BFI is only in 50% granularity (8ms persistence steps), though the new 2019 LG OLEDs can do BFI in 25% granularity at 60Hz and 50% granularity at 120Hz (4ms persistence steps)
Except for the virtual reality OLEDs (Oculus Rift 2ms persistence), no OLEDs currently can match the short pulse length of a strobe backlight just yet, though I'd expect that a 2020 or 2021 LG OLED would thus be able to do so./QUOTE] - <edit by elvn: > they dropped bfi from the 2019 models but the numbers apply to 2020 oleds as 15% 40% it seems.
Black duty cycle is independent of refresh rate. However, percentage of black duty cycle is directly proportional to blur reduction (at the same (any) refresh rate). i.e. 75% of the time black = 75% blur reduction. Or from the visible frame perspective: Twice as long frame visibility translates to twice the motion blur.
Does not matter if full strobe or rolling scan, as it is per-pixel duty cycle.
Note: That said, non-global illumination can cause artifacts (e.g. skewing during scan of any CRT, OLED (including strobed and nonstrobed rolling scans) or nonstrobed LCD -- when viewing http://www.testufo.com/blurtrail will skew in nonlightboost at 32pps -- but stops skewing in lightboost or global strobe. Also, if viewing animation on iPad, rotate display until you see line skew)
Bell curve strobe rather than squarewave strobe can be useful and may look better for some applications other than VR, or slower motion/unsynchronized(VSYNC OFF) motion. As a slight persistence softening can reduce the harshness of microstutters from non-perfect refreshrate-framerate synchronization. But other ultrafast refresh-rate-synchronized motion, minimum motion blur dictates point strobing (as short as possible persistence, which is electronically easier with squarewave...just turn off pixel automatically mid-refresh....independent of refresh rate exact interval....aka Rolling Scan).
There is no such thing as "180Hz internal operation" as Oculus is already 80-90% black duty cycle (2ms persistence, despite 1/90sec = ~11ms refresh cycles) -- it is just a pixel-turnoff time delay, in a rolling scan algorithm. You adjust persistence simply by chasing the off-scan closer to the on-scan. See high speed videos. Screen gets darker the more you shorten a rolling scan OLED persistence, and you may get into color nonlinearities as active matrix transistors turning on/off OLED pixels aren't perfectly squarewave at the sub-millisecond level.
Good VR makes perfect framerate-refreshrare vsyncing mandatory, unfortunately for the Holodeck immersion. No ifs, buts, no protest, it is just the way the cookie crumbles for VR. In this case, striving for CRT-style curve strobing (instead of square wave strobing) is rather useless UNLESS you need it to hide imperfections (e.g. Flaws in the display) or reduce eyestrain at lower strobe rates.
1ms of persistence translates to 1 pixel of motion blur for every 1000 pixels/second motion. (We call this the "BlurBusters Law") For motion on a 4K display going one screenwidth per second, at 1ms strobe flashes, all 1-pixel fine details gets motionblurred to 4 pixels from the act of eyetracking against the visible part of the refresh cycle.
This can also be observed in action by the motion-induced optical illusion that only appears during eye tracking: http://www.testufo.com/eyetracking
If you have an adjustable-persistence monitor:
You can even see the relationship between persistence and motion blur, then use your persistence adjustment (strobe duty cycle adjustment, e.g. ULMB strobe adjustment, BENQ Blur Reduction strobe length, etc) while watching http://www.testufo.com/blurtrail ... The line blurring goes exactly twice the blurring (no matter the refresh rate) for double the persistence, and follows BlurBusters Law (1ms strobe length = 1 pixel added motion blur during 1000 pixel/sec motion, but becomes 2 pixels of blurring at 2ms persistence)
Hz and persistence can be unlinked/unrelated thanks to strobe duty cycle adjustment. But if you wanted to completely eliminate black periods, a 2ms persistence display with no strobing, would need to run 500fps@500Hz flickerfree to match Lightboost 2ms, or Oculus flicker rolling scan 2ms. This is because 1 second divided by 2ms equals 500 visible distinct frames needed to fill all 2ms slots of 1 second to avoid any blackness, while keeping motion of each frame perfectly in sync with eye movements. Even a 2000fps@2000Hz display (needed for 0.5ms full persistence woth zero black cycle) would still have human-visible motion blur in extreme conditions (e.g. Fast head turning with 4K or 8K VR while trying to read fine text on a wall). Oculus knows this. Michael Abrash confirms the relationship between persistence and motion blur.