One thing I should add to this topic is GtG response (pixel transition time) and MPRT response (pixel persistence).jorimt wrote:On the OLED VRR subject, it should be noted those already sensitive to lower framerate judder on LCD displays during VRR operation (and film content playback), will likely be even more put off in this respect due to OLED's virtually instantaneous pixel response.
These are two different pixel response time measurements. Now that manufacturers are often measuring both, and the more honest manufacturers are displaying both numbers, it's worth explaining the two numbers. Finally, about time!
GtG = Grey To Grey = pixel transition time = length of time a pixel takes to change color for.
MPRT = Moving Picture Response Time = pixel static time = persistence = length of time a pixel stays continuously visible for
Read that carefully. GtG is essentially pixel change and MPRT is essentially pixel non-change.
(They can blend/add into each other though, e.g. very slow GtG lengthening MPRT).
GtG that is a significantly percentage of a refresh cycle, adds visible motion blur. Below that, GtG becomes unimportant. While OLED has almost no GtG, the fact remains is OLED is hugely bottlenecked by MPRT response. The MPRT of a non-strobed OLED and non-strobed TN LCD is darn near virtually identical.
I also point readers to OLED Motion Blur: Why Do Some OLEDs Have Motion Blur?.jorimt wrote:E.g. LCD pixel response causes blur (in varying amount depending on the given GtG of the panel) between high persistence (low framerate: <30 under) frames, and OLED has pretty much zero blur, which results in much more obvious judder/frame doubling effects in the same instances.
One needs to turn on the Black Frame Insertion feature of an OLED to successfully pass the TestUFO Panning Map Readbility Test.
- The new 2018 LG OLEDs can go as low as 4ms persistence, which is enough to read street name labels at 480pps.
- You need 2ms persistence to be able to read the labels at 960pps
- You need 1ms persistence to be able to read the labels at 1920pps.
As a rule of thumb, you need (x/1000sec persistence) to read 6-point street labels at (x times 2) pixels per second.
None of the 2017 LG OLEDs can pass the TestUFO Readability Test at motion speeds faster than roughly ~240pps. That's the MPRT response bottleneck. The majority of OLED generates exactly the predicted display motion blur that almost equals the MPRT(100%) mathematics of Blur Busters Law -- the exact amount of motion blur is uncannily darn nearly exactly equal to Blur Busters Law.
Mathematically, a screen can have 0ms GtG while having 16.7ms MPRT. Pixel transition time can be completely different from pixel visibility time (persistence) -- how long a pixel is continuously lit for between refresh cycles, adds to motion blur.
Eye movements whenever a pixel is turned on, smears that pixel across retina, generating extra display motion blur caused by static refresh cycles being smeared across your retinas, as testufo.com/eyetracking still shows up "perfect motion blur" on an OLED -- the "eye tracking motion blur" optical illusion, in fact, is actually sharper on an OLED than on an LCD, because there is no more GtG to muddy up the MPRT. The sharper the checkerboard, the more pure the Blur Busters Law is (1ms of pixel visibility time = 1 pixel of motion blur per 1000 pixels/second)
Bring out your Galaxy phone, an iPhone X, or start up an LG OLED HDTV, and load testufo.com/eyetracking and select "Checkerboard" .... The OLED motion blur is still there. The GtG blur is gone, but the MPRT blur is still there. Don't believe me? I'll wait, play this motion test, and if you see a checkerboard, then you have display motion blur, guaranteed, period..
Certainly the blur is so low on many OLEDs, and there is no visible GtG blur, so many understandably say OLED has no motion blur. But that's only true for GtG blur. The MPRT/persistence blur is there, and if you see any form of any square checkerboard optical illusion, that's display motion blur.
The only way to reduce MPRT is to reduce pixel visibility time.
Reducing pixel visibility time for a frame is done by:
1. Pulsing the pixel briefer (adding black periods between pixel visibility time, e.g. 2ms strobe flash at any Hz = 2ms motion blur)
2. More frames in their refresh cycles with no black periods in between (e.g. [email protected] = 1/480sec persistence = 2ms motion blur)
3. Combination of both of above.
Also, OLED has no frame doubling effects when no black frame insertion is used.
The frame doubling effects occur because the linear motion blur (Adobe Photoshop style) is "chopped up" by the black time, e.g. 30fps at 60Hz impulsed, 60fps at 120Hz impulsed. Multi-impulsing a refresh cycle in any manner (whether it be by PWM dimming, or via a framerate lower than refresh rate / strobe rate) creates an impression of duplicate images. It's like an Adobe linear motion blur except that the blur is interrupted in between the duplicate images because "the frame is not continuously visible in one smear".
The frame doubling effect only appears if you turn on the OLED's black frame insertion feature (or if the particular OLED uses any PWM dimming feature like some smartphones do) -- and have a frame rate (or refresh rate) below the flicker rate.
By default, OLED doesn't do this unless it's in a PWM-mode or BFI-mode.
It's simply a continuous blur equalling this: