Join Date: Dec 2012
Location: Near Cambridge, UK
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Percentage difference is frequently not understood, but can contribute to viewing problems if too high. The percentage difference is the difference betweenn the left and right images in relation to the screen size. Measure the distance between the maximum negative and positive parallax in the image and then calculate what percentage of the screen size that represents. Most people can tolerate 5-6% difference and some slightly more, but once images start to approach 10%D, then your eves are unable to resolve the image. This often happens when there is a lot of negative parallax as some film makers seem to feel that everything shouuld fly out of the screen at you. The effort of tryng to resolve these images and changing focus from high negative to positive can quickly induce headaches.
If you can reduce the difference at the projector, then you can cut down the side effects, but if the %D is too high on the disc, it may be impossible to correct. A lot of the novelty 3d films use gimmicky out of screen effects and these are often the ones that cause the most problems.
I find that quit a lot of blockbuster 2d movies give me a headache when they contain very fast scene cutting and high speed action shots, causing me to constantly change focus and eye movement. With 3d, quick changes in requirement for depth perception can have the same effect although not being so obvious to the viewer. It's something that some 3d producers don't seem to appreciate fully.