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Do active shutter glasses produce depth problems with motion?


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#1 Karel Bata

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Posted 23 June 2010 - 12:17 PM

It seems to me that if you're filming Left and Right frames at the same you should mimic that later when viewing. However active shutter glasses rapidly switch between eyes. This means that one eye is ahead of the other - left, right, left, right, etc. Not a problem for viewing a still life, but once an object is moving, might the horizontal displacement be misinterpreted as a depth cue?

Bit difficult to describe what I'm thinking here without a diagram, but imagine a point of light behind the screen plane where the L and R images are displaced by 10 pixels. It then moves on the x axis at 8 pixels per frame. You'd then get the point being seen 8 pixels along (left eye), then 18 pixels along from that (right eye), like so:
8 18
16 26
24 34
32 42 etc
But what if the brain decided to fuse the images closest to each other? You get:
18 16
26 24
34 32 etc
yielding a displacement of 2 pixels and shifting the perceived depth to somewhere else. :blink:

Did all that make sense? So, is this seen as a problem at all...?
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#2 Phil Connolly

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Posted 23 June 2010 - 01:54 PM

Generally on fast movement all single projector digital 3D systems cause artifacts on fast movement due to the sequential frame display. With triple flash - isn't not too bad and most people don't find it objectionable. Its not just a problem with active shutter glasses. Real-D and Dolby 3d systems have the same issue with alternating left and right eyes.

I guess a difference of 2 pixels may not be enough to create a noticeable depth cue, but the brain may have to work harder to fuse the two images.

Dual projector 3D and 35mm Technicolor 3D are claimed by some to be easier on the eye, because both eyes images are on screen at the same time.
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#3 Karel Bata

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Posted 24 June 2010 - 04:00 AM

Cheers! I saw a demo of a sequence of Alice cut for 2D followed by the same in 3D projected using shutter glasses. The 3D was much more immersive, but the motion looked really bad to me. Would have liked to have seen that in Technicolor 3D for a comparison.
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#4 Phil Connolly

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Posted 24 June 2010 - 03:48 PM

Cheers! I saw a demo of a sequence of Alice cut for 2D followed by the same in 3D projected using shutter glasses. The 3D was much more immersive, but the motion looked really bad to me. Would have liked to have seen that in Technicolor 3D for a comparison.


Yeah, I'm curious about Technicolor 3d, but I don't know of any Uk installations yet. The only LCD shutter glasses 3d I've seen was Imax 3D. Which I belive ran at 96hz rather then the 144hz of digital 3D - the 3d was good but the motion was very juddery.
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#5 Keith Mottram

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Posted 29 June 2010 - 04:31 PM

Hi Karel,

not noticed any problems in this respect on the 50" panasonic that I use. Would say that overall I think active give a far superior experience than passive sets, in terms of richness of experience...

Keith
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#6 Karel Bata

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Posted 30 June 2010 - 06:03 AM

Oh yes, better without a doubt.

Maybe the example I gave above is overly complicated. Imagine an object with a L/R separation of 20 pixels moving at 20 pixels a frame. If L and R are projected simultaneous there's no prob, but if it's alternating L R L R then the brain may be tempted to fuse the two that overlap and move the image to the screen plane.

Maybe you could create a simple test there..? if you can be bothered that is... :D
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#7 Keith Mottram

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Posted 30 June 2010 - 07:01 AM

Oh yes, better without a doubt.

Maybe the example I gave above is overly complicated. Imagine an object with a L/R separation of 20 pixels moving at 20 pixels a frame. If L and R are projected simultaneous there's no prob, but if it's alternating L R L R then the brain may be tempted to fuse the two that overlap and move the image to the screen plane.

Maybe you could create a simple test there..? if you can be bothered that is... :D


I dunno the rate the shutters move at probably kills this issue... at least in practice... no i cannot be bothered at moment anyway!
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