Panasonic pushing motion portrayal [scanning backlights]

[Neo]

The topic is relevant to a scanning vs strobe so no new thread really needed. The scanning I'm referring to is blanking not simply rendering output. More specifically I'm interested in how blanking the backlight can hide the tearing/shutter roll effect.

Instead of rendering a whole frame and then blinking on a scanning band for low persistence to show only a small part of that whole frame, each band could be an independent sub-frame.

For example:

100 fps output. 10ms per frame. 10 band scanning top to bottom 1ms each. Instead of a single frame/moment in time being sequentially revealed from top to bottom over 10ms, each band would be a completely new updated view of the scene. Such as a vertical bar moving across the screen from left to right where the scanning band renders where it is at each millisecond rather than where it was in the very first "whole" frame. Instead of rendering and displaying 10x more whole frames, each visible scanning band is treated like a 1/10th-sized (or smaller) "subframe" which uses the sequential nature of scanning to present a more precise view of the updated scene. It's like syncing (sub)framerate with (sub)refreshrate where the visible scanning band is the effective refresh rate presented to the eye. I know there are issues with making perfectly sharp scanning segments with current leds (oled could fix that?) but wouldn't blanking the backlight hide any tearing effect? Or would the limiting factor be the eye, such as a need for the rendered image to be a perfect aligned whole image.

[Chief Blur Buster]

I know there are issues with making perfectly sharp scanning segments with current leds (oled could fix that?)

Yes, OLED rolling scans are not an issue. They actually work well:


(From an OLED paper, around section 20)

I've linked to a high speed video of an OLED rolling scan.

but wouldn't blanking the backlight hide any tearing effect?

No -- Your eyes are in different positions as you track, and no matter how you illuminate, if you illuminate a specific part at a disjoint to another specific part (even temporally), a disjoint is noticed.

Or would the limiting factor be the eye, such as a need for the rendered image to be a perfect aligned whole image.

At current limited monitor/GPU technology, current limiting factor is eye, and human dependant. Tearing is still noticeable even at 960 frames per second, too (see ezQuake thread in Area51).

At 4000 pixels per second mouse swipe (fast flick 180 degrees) tearline offsets can still be 4 pixel skew during 1000fps (4000pixels / 1000fps = tearline of 4 pixel skew).

Here is what tearing looks like during a fast flick 180, at 960 frames per second in ezQuake on a 160Hz CRT:
http://forums.blurbusters.com/viewtopic ... 1257#p1207

[Neo]

Ah OK.

That forum link was a good call because the same-ish idea popped up here:

I wonder if the image being distorted in real time to follow the inputs would be better (you could push the hypothesis to the point where there are as many frames as there are pixel ie "racing the beam" as Abrash or Carmack said)...

Infinite framerate on a finite framerate display -- where each pixel is a real-time representation of the 3D scene, as the display scans out. Interesting thought.

[OttoNaumann]

Does somebody know if Panasonic employ scanning backlights on the LFX60? I think it would be necessity for 2000cd/m2 brightness without some uniformity problems but really I am not sure

[Chief Blur Buster]

Does somebody know if Panasonic employ scanning backlights on the LFX60? I think it would be necessity for 2000cd/m2 brightness without some uniformity problems but really I am not sure

Do you mean 200cd/m2 average brightness?

Depending on your target persistence (amount of motion blur reduction), you may not need 2000cd/m2 backlight flashes to achieve an average of 200cd/m2 of common television watching. Most scanning backlights use a 4:1 duty cycle or similar, rather than 10:1, while adjusting brightness can adjust the duty cycle on some of these (clearer motion at dimmer brightness settings). That said, more brightness, the easier to achieve low persistence (less motion blur) via strobing/scanning/black frame insertion.