55
Chapter
4
Adjustments
and
Settings
for
Recording
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
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.
Convergencepoint
Left-lensimage
Right-lensimage
Parallactigangleindepth
Parallacticangleforpopout
• Extreme parallax between left and
right images is demonstrated in the
illustration above.
Parallaxforpopout
Parallax: Approx. 3 % or less (any screen size)
Parallaxindepth
For a screen of 77-type or less
Parallax: Approx. 3 % or less
For a screen of 77-type or more
Parallax: 50 mm or less
