Quote:
Originally Posted by
infamous_pb 
I am now convinced that it is not a blooming problem with 3d but something within the 3d viewing itself. What I thought was blooming was actually seeing double images. When viewing 3d, on some objects, lets say a stick from a tree, would have a vague double image of it to the left and to the right. If I cover one of my eyes, I only see the stick and the double image of the stick to the left. If I open that eye and close the other, I see the stick and the double image of the stick to the right. Both eyes open - then its back to the stick and a double image of it to the right of it and another to the left.
Is this normal?
It doesn't do it to every object on the screen. Just maybe one or so at a time. Sometimes for a few seconds, everything would be perfect and there are no double images.
Any ideas? Or is this what all 3d TVs do?
This is the phenomenon known as 'crosstalk'. Unfortunately it's a side effect of the display technology. LCD displays tend to have more problems with crosstalk than some other tech displays. Supposedly, DLP has very little (eg. Mitsu 3D RPTVs) and plasma (Panny VT25) also has significantly less crosstalk. I can confirm that the Panny shows hardly any crosstalk, but haven't seen a Mitsu 3D TV.
The reason crosstalk happens has to do with the image refresh rate and how quickly the images are erased from the display. There is an inherent delay in how quickly a displayed image fades out. The faster this happens, the less crosstalk is visible. With LCD technology, although they've made significant strides in reducing this delay (called the on-off response), it is still several times longer than with the other technologies.
With the shutter glass 3D, basically, the TV is alternately displaying the right and left eye images, while simultaneously blocking the image to the opposite eye with the shutter glasses. So the TV brings up the right eye image, the shutter glass blocks your left eye from seeing it, then the TV flashes the left eye image and the shutter glasses simultaneously switch to open the left eye while blocking the right eye, so you alternately see right followed by left eye images and your brain puts the images together to form the stereoscopic illusion.
If however, the right eye image has not completely faded out by the time the left eye image is displayed and the glasses open the left eye lens, you see the remnant of the right eye image as a ghostly outline. To achieve the stereoscopic effect, the left and right eye images are slightly displaced relative to each other (parallax), which is why when you close one eye, the ghostly outline is on one side of the stable image and if you switch and close the opposite eye, the ghostly outline is on the other side. With both eye open, you see the outline on both sides.
The absolute clearest 3D presentation I've seen thus far was years ago at Universal Studios in Florida. At the time, I believe they were still using what I call 2nd generation 3D movie technology (1st generation = anaglyph/red-blue glasses, 2nd gen = one vertically polarized, one horizontally polarized lens, 3rd gen = circular polarization, clockwise and counterclockwise, 4th gen = LCD shutter glasses, 5th gen = autostereoscopic, no glasses required).
With the Universal Studios presentation, the 3D was incredibly crisp and clear as long as you kept your head perfectly level. Tilting your head left or right resulted in seeing double images, but if you kept your head straight, there was one scene in particular where a CGI cartoon character flies around and then appears to stop about arms length from you and then proceeds to extend its nose at you. The image is so clear, your eyes are telling you that it is a real object, floating in mid-air within grasp, and its nose is 6 inches from your face. I found it particularly amusing that when this scene occurred, EVERYONE in the theater (me included) reached out and started grasping at thin air trying to touch the cartoon character that your eyes swore was right in front of you. There was no crosstalk in ANY part of the presentation. In contrast, the other 3D presentation I watched on that trip (this was back in '94), Michael Jackson's Moonwalker was a horrible mess of crosstalk and doubled images.
It's pretty sad that I could see crosstalk on a couple of scenes in Avatar 3D (I watched it twice, in both Imax 3D and RealD 3D), considering there was a pristine 3D presentation 16 years ago. In Avatar's case, I believe the crosstalk might have had something to do with the RealD polarizer going out of sync for a brief period.
Theater RealD 3D is achieved by placing a circular polarizer in front of a digital projector. The projector shows 144 frames per second and alternates between left eye and right eye images with the RealD polarizer switching between clockwise and counterclockwise polarization between each frame. The image is reflected of a silver screen (which retains the direction of the polarization) and the viewers wear circularly polarized glasses where one lens is polarized clockwise and the other is counterclockwise. If the polarizer lens in front of the projector loses sync for some reason, then it's possible for it to not cut out the images meant for only one eye.
BTW, AFAIK, for the folks who were wondering, the RealD capability of the 554 is not of the circularly polarized variety. I believe it just refers to the RealD side-by-side encoding format, which means it won't work with passive glasses.
Max
