Originally Posted by Masta Squidge
but your brain is still processing the individual frames, even when they are coming at 60 hz. It just takes this data, and feeds it to your consious mind as a continuous stream.That is why nearly everyone agrees that 120 and 144hz monitors look fantastic.
You might want to study up on some of the motion blur mechanics. You're close on many things, but I wanted to point a few subtle things (e.g. to understand certain situations why a lower-refresh-rate display can have less motion blur than a higher-refresh-rate display -- and NOT because of LCD pixel response speed). BTW -- eyes do not actually process "individual frames" -- but yes, it is a continuous stream.
As part of BlurBusters.com blog, I did some pursuit camera measurements of motion blur on a modern LCD, and found full order-of-magnitude differences in motion blur:
(from 60Hz vs 120Hz vs LightBoost
Motion blur (when tracking moving objects on a display) is dictated by how long each specific static frame is displayed on the screen. As your eyes track moving objects on a screen, your eyes are in a different position at the beginning of a refresh than at the end of a refresh -- so the individual frames are blurred across your vision. Your eyes aren't digital stepper motors -- your eyes are continuous tracking in an analog way, while the frame steps-forward in discrete steps (Hz and refresh rates are artifical inventions from a human vision perspective -- the real world has no refresh rate.) Reading up about sample & hold science
is useful to add to this understanding.
Why does CRT 60fps@60Hz have less motion blur than LCD 120fps@120Hz? (Hint: It's not because of LCD pixel transition speed limitations -- this is already successfully bypassable
via a strobe backlight such as LightBoost -- instead, see Why Does Some OLED Have Motion Blur?
as a good explanation why instant-pixel-response displays can still have lots of motion blur)
For example, the ASUS VG248QE is rated at 1ms pixel transition speed, and the Sony GDM-W900 CRT is about 1ms phosphor cycle (illuminate-and-decay). Same number, but the W900 has vastly less motion blur. Why, even though the ratings are similar now? Unless the VG248QE's LightBoost strobe backlight mode is enabled -- then they are roughly equal in motion blur (testimonials from former CRT users
). Sometimes it's hard to understand until you realize the motion blur during eye tracking of moving on-screen objects, is actually proportional to the amount of time each frame is displayed onscreen. (The sample and hold effect). Truly, when the time of LCD pixel transition times (from one color to next, e.g. 2ms) becomes far less than the time of one frame (one refresh, e.g. 16ms), it no longer dominates motion blur -- other factors such as sample-and-hold now dominates motion blur instead.
Also why does CRT 60fps@60Hz have roughly the same amount of motion blur as CRT 120fps@120Hz? Whereas LCD 120fps@120Hz has half the motion blur of LCD 60fps@60Hz? Answer: That's because the phosphor decay (flicker time) is virtually unchanged at all CRT refresh rates. Whereas, it has a more dramatic effect on LCD, since the LCD sample-and-hold effect halves every time you double the refresh rate.
So, the only way to reduce this motion blur bottleneck by the display, is to reduce the amount of time each individual frame (refresh) is displayed for. Either by:
(1) Adding more Hz; or
(2) Adding black period between Hz (e.g. CRT flicker, LightBoost flicker, plasma flicker, black frame insertion, scanning backlight).
Then it all suddenly makes sense -- becomes simpler to understand.
It explains all the motion blur questions above very conveniently; and is consistent with the scientific stuff already known (and it's well known that flicker reduces motion blur -- and photographers already know shorter shutter speeds means less motion blur in photos, etc. In other words, the brief flashes of a flickering display -- essentially behaves as the metaphorical shutter (for each frame/refresh) that prevents tracking-based motion blur -- eyeball movement versus camera movement -- remarkably similiar blur mechanics).
Either of the two above methods, (1) or (2), shortens the amount of time a frame is displayed for, and thus reduces the eye-tracking-based motion blur. Sample-and-hold (especially LCD) is the cause of extra motion blur when the human eye tracks moving objects. Even at 120Hz and 144Hz which is not as clear as a CRT, to my eyes and many others. Fortunately, fixable by LightBoost, a strobe backlight (see 1000fps high speed video of LightBoost
Another good article is TFTCentral: Motion Blur Reduction Backlights Including LightBoost
-- about adding the CRT effect to LCD displays, as an additional method of reducing motion blur even further.
Also, some HDTV's have a scanning backlight (e.g. Sony, Panasonic, Samsung
) to reduce motion blur (via flicker effect) above and beyond just using interpolation (adding Hz).
Points of diminishing returns definitely do occur for higher Hz, obviously. However, they don't suddenly stop. Even 480fps@480Hz can have motion blur (for a sample-and-hold display)! High speed motion (framerate matched with Hz) moving at 1920 pixels per second has 4 pixels of motion blur during 480Hz sample-and-hold (1920pixels/sec divided by 480Hz, equals 4 pixels of tracking-based motion blur). it is amazing how high refresh rates can go, and we can still see motion blur, if we look hard enough. Likewise, for the photography metaphor -- Sports photographs taken using a 1/480sec shutter speed can still have motion blur, if the camera's panning sufficiently fast. Obviously, it is a hell a lot easier to eliminate motion blur by using flicker (CRT style), since we can reduce motion blur without increasing Hz (preventing the need for more powerful GPU's). As you can see, for some people, plain 120Hz or 144Hz still has too much motion blur, even if they are still a big improvement over 60Hz.
Yes, adding motion blur can be good and artistic. Special effects, etc. Other times, it's quite undesirable (e.g. lack of motion blur improves reaction times during racing games & first person shooter games). This post is just simply to explain motion blur mechanics of displays. (To correct some misconceptions about how display motion blur works).
Meanwhile, back on topic -- the SEIKI 4K HDTV supports 1920x1080p at 120Hz native refresh rate -- though it does not have a strobe backlight to reduce motion blur even further.Edited by mdrejhon - 6/20/13 at 1:31am