Temporal Aliasing (Tessive Time Filter)

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Temporal Aliasing (Tessive Time Filter)

Post by ldmelsa » 04 Feb 2014, 16:52

Nice video that explains "temporal aliasing"

Forum member James Freeman was talking about mechanical shutters - well this Tessive Filter is an electronic global shutter.

I know it doesn't have anything to do with monitors, but the same principals apply.
This filter is used by videographers that want smoother motion at 24FPS, and videographers using a camera with a rolling shutter.

Chief Blur Buster talked about decay ramp versus square-wave strobing. This "electronic global shutter" has a decay (obviously - that's the point of the thing). Its like shutter glasses for cameras :)
Just thought it's interesting.

BTW - I'm new here and this is a great site that addresses one of the biggest inherent problems with panel displays - high persistence. I'm so glad there is a forum/site devoted to it. Thanks!

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Re: Temporal Aliasing (Tessive Time Filter)

Post by orik » 04 Feb 2014, 17:14

I wonder if you could use one of these on a light source to create a strobing projector.

I'm thinking of the application in a project like this: http://forum.allinbox.com/aspectgeek/Pr ... 9774_1.htm

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James Freeman
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Re: Temporal Aliasing (Tessive Time Filter)

Post by James Freeman » 05 Feb 2014, 01:06

Thanks ldmelsa.

This is exactly what I ham about to do. ;)
I already bought (ebay) Active 3D Glasses and Signal Generator with PWM (resolution 0.01Hz) two weeks ago.
Just waiting till they arrive (from china).

http://www.liquidcrystaltechnologies.co ... utters.htm
Nothing special here, just a Liquid Crystal Shutter Panel with some Signal Generator (SG) to open and close the panel (5V).
The LCD used in the glasses can switch up to 1000Hz (1Khz), my Signal Generator can go from 0.01Hz-2MHz, so it'll be fun experiment.

The problem is my method will not be in sync with the display, BUT 0.01Hz precision will be enough to fine tune the SG+glasses to the screen.
Yes, there will be drift (resulting in tear) over some time (hopefully long), but it can be easily fixed by adding/subtracting frequency for some short time till the image moves back to place then returning to the original frequency.
Besides its only for experimenting and learning.

:geek: <- That's me in custom SG+PWM+Active 3D glasses to Bust the Blur...

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Re: Temporal Aliasing (Tessive Time Filter)

Post by ldmelsa » 05 Feb 2014, 01:41

That's very interesting James. The thing with sync is that the "Time Filter" will synch to a genlock output from a camera. If you can get a sync signal from your source, and convert that to genlock, who knows? I think one can get sync signal from a component Y'UV output. I think one can get a sync signal from the luminance value (Y). Don't quote me one that :? But that's how they do it on this Sony cam http://tessive.com/camera-system-support/

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Re: Temporal Aliasing (Tessive Time Filter)

Post by Ahigh » 08 Feb 2014, 02:09

Great post! This is a great explanation of the aliasing effect of limited exposure times. I think many people filming use continuous exposure times (360' shutter in his nomenclature), and in that case, the problem doesn't manifest as much. But for film guys who want a little bit more detail on the slower moving objects without aliasing on the faster moving objects, this is genius.

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