What is parallax?
A human’s stereoscopic viewing takes advantage of the brain’s ability to process information from the left and right eyes of two images seen from their respective perspectives. The misalignment of the two images is called binocular parallax.
Mainly binocular parallax is used by 3D equipment to create the feeling of stereoscopic images. When shooting, the images from the left and right lenses are misaligned because of the difference in the positions of the lenses as well as in the directions of the optical axes. This misalignment (called parallax) changes according to the distance of the subject being shot (illustration at right).
If parallax is excessive, it is difficult to fuse the two images within the brain. This may produce a double image, create a feeling of strangeness, etc., causing eyestrain.
Limiting the parallax appropriately during shooting is important for comfortable 3D viewing.
Are there guidelines for appropriate parallax?
There are two guidelines for parallax.
A Parallax: 3 % or less the effective width of the screen It is usually said that a parallactic angle within 1 degree is preferable for comfortable 3D viewing. The parallactic angle, here, means the difference between the angle of convergence when a viewer watches a point on the screen and the angle when he or she watches an object popped out or recessed from the screen. A large parallactic angle makes it difficult for the viewer to perceive a stereoscopic image, causing eyestrain.
Assuming that people view 3D images from a distance three times the effective height of the screen, a parallactic angle of 1 degree corresponds to misalignment of approximately 3 % the effective width of the screen. This leads to one of the guidelines for parallax, which is to limit horizontal misalignment to within 3 % the effective width of the screen.
B Parallax in depth: 50 mm or less
Parallax in depth is created when an image from the right lens is displayed to the right and an image from the left lens to the left on the screen.
If the value of this parallax exceeds the pupil distance of a viewer, it will cause eyestrain.
In consideration of individual differences of viewers such as age and pupil distance, setting parallax to within 50 mm is preferable.
Parallax in depth is related to screen size. For a 16:9 screen, if the screen size is 77‑type or less, limiting parallax to within 3 % the effective width of the screen means that parallax in depth will not exceed 50 mm. If the target screen size is 103‑type, limit parallax to 2.2 %. For a 200‑type screen, limit parallax to 1.1 %.
How to operate this camera
The 3D assist function of this camera (page 56) provides a guide of distance ranges from the subject for achieving appropriate parallax. Referring to the guide, change the layout of the subject and check the parallax value (% effective screen width), using a monitor.
Convergence point
Parallactig angle in depth
Parallactic angle for pop out
•Extreme parallax between left and right images is demonstrated in the illustration above.
Parallax for pop out
Parallax: Approx. 3 % or less (any screen size)
Parallax in depth
For a screen of
For a screen of
Adjustments ChapterandSettings 4rding rfoRec
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