Among the existing methods,
I choose to apply the parallel view method for the pictures
not exceeding 200 pixels in width per view, and the cross-eye
view method for the larger views.
For viewing 3D pairs, as
slides or prints , see the page viewing
PARALLEL VIEW METHOD
With each view of 200 pixels, the
width on the screen of a computer at 72 pixels per inch
is 70mm for each. It is the maximum which is possible to
superimpose without a specific viewing device.
The left eye
looks at the left view placed on the left.
The right eye
looks at the right view placed on the right.
A mask 150x60mm with two windows
40x25mm helps viewing. The distance between the two windows
is 20mm so the distance of axis of the two windows is equal
to the space between the eyes. Two slide frames could be
used also as a mask. With experience, this mask is unnecessary.
Each view must be looked at with
the corresponding eye. It is sometimes necessary to lean
the head from right to left to get the vertical matching
of the objects.
CROSS-EYE VIEW METHOD
The left eye
looks at the left view placed on the right.
eye looks at the right view placed on the left.
Follow the method on the right
A cardboard mask may ease to cross
To make this mask, open this drawing
and calculate the side C of
the square to cut in accordance with the lengths as shown.
C = E.M./ (E + M)
E is the distance between
eyes and M the width of one picture.
In the example below, M=100mm,
E=65mm so C = 40 mm.
Position the mask so that when
closing the left eye, the right eye watches exactly the
right view through the window. Do the same with the other
eye. Set the mask forward or backward such that each view
is matching the window.
Then look at with the two eyes
through the window. It is sometimes necessary to lean the
head from right to left to get the vertical matching of
Quickly close alternatively each
eye, and then open both. Or squint to the middle of the
bottom edge of the window before to look at through.