What is convergence point adjustment?
•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 Parallactic angle for pop out: 1 degree or less
A parallactic angle is produced between the left and right lenses and the subject (illustration at right). It also changes according to the distance of the subject being shot.
It is usually said that a parallactic angle for pop out within 1 degree is appropriate for comfortable 3D viewing. 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 %.
Convergence point | Parallactic angle |
in depth | |
Parallactic angle | Parallactic angle |
| |
| for pop out |
Parallatctic | Shooting |
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 77-type or less
Parallax: Approx. 3 % or less
•How to operate this camera
⇒The 3D guide function of this camera (Page 38) provides a rough guide of distance ranges from the subject for achieving appropriate parallax in two cases: for an intended screen size of 77‑type or less, and for 200‑type. Referring to the guide, change the layout of the subject or adjust the zoom and convergence, so that the subject can be shot within the distance range shown by the 3D guide function. Check the parallax value (% effective screen width), using a monitor.
For a screen of 77-type or more
Parallax: 50 mm or less
39