UPDATE: I revisited this subject because the comments on this post made it clear there was still a lot of confusion on this topic. Read the clearer explanation here.
I’m interested in 3D technology and lately there have been a lot of interesting developments. One of the most promising new 3D technologies for the home is imho the kind of passive 3D technology that LG and others are introducing to their new screens where the screen itself is taking care of delivering the images for the left and right eye to the separate eyes, instead of the glasses. This technology is called passive 3D because the glasses are simple passive polarized lenses, instead of battery powered active shutter glasses.
But as sometimes seems to happen there is this myth that keeps perpetuating itself that to me seems to be blatantly wrong if you just stop and think about it for a second, but for some reason nobody does that and the myth just gets repeated over and over again. The myth is that:
“Passive 3D offers inferior resolution because the amount of display lines gets halved”
This seems to make sense at first. Only half the pixels is sent to each eye. The other half is reserved for the other eye. So resolution is halved right?
Well yes. Compared to 2D it sure is. But this is always mentioned as a disadvantage of passive 3D when compared to active 3D and I think that is totally misleading. Active 3D *also* halves the resolution, it just does that over a different dimension (time vs space). Active 3D halves the temporal resolution whereas passive 3D halves the spatial resolution. In the end both technologies display 2 frames on the same screen that would show only one frame in 2D mode, so both half the resolution compared to 2D.
Just have a look at the diagram below and I think it will be completely clear that active 3D does not show a single pixel more than passive 3D does. It will also be clear that passive 3D can potentially give a much more stable picture, with less flickering.
For each technology we show 4 frames of 3D animation. The white pixels are showing the image and the black pixels are ‘blocked’ or ‘blacked out’. On the left we see active 3D. Here alternating the left and right eyes are shown a picture and a black frame. On the right we see two ways of doing passive 3D, either alternating horizontal lines or a checkerboard pattern (theoretically columns could be possible too but I haven’t heard of a TV model doing this so I left that out). As you can clearly see with both the passive technologies your left and right eyes combined get exactly the same amount of displayed pixels (as opposed to blocked or blacked out ones) as with active 3D. But the patterns on the right are much more regular than the alternating pattern on the left, which should result in a much more stable, flicker-free picture.