CHAPTER 17CLOSE-UP STEREOGRAPHY
(Macro - Micro)HERE HAS BEEN A GREAT DEAL of confusion regarding close-up
T work in stereo. Indeed there have been many “laws” cited
which are not laws at all, but simply principles arising from a de-
sire to present the most attractive appearance in the finished
stereogram. For example, there are the many rules which give the
minimum working distance at nearly every conceivable distance
between three and ten feet. In reviewing such statements, let us
consider the optics of orthostereo. The angular values of the orig-
inal direct vision, including that of convergence, are substantially
duplicated in the camera. Of course, exact duplication is not pos-
sible for several reasons, including the difference among individ-
ual interpupillaries, the greater base of several types of cameras
and the like. The important factor is that these slight discrepan-
cies exert no appreciable visual effect.
Therefore it is obvious that the actual minimum working dis-
tance is the minimum distance of comfortable direct vision, or
approximately 16 inches. It is well known that two widely fa-
vored cameras, the Realist and the Verascope, have focusing scales
calibrated to two and one-half feet and two feet respectively;
and that hundreds of owners use the camera at these distances
with full satisfaction. There is a reason for avoiding extremely
close work, but it is nothing more than an incidental limitation
imposed by the camera.
In direct vision we have learned to concentrate upon that ob-
ject which is the center of interest, and largely to ignore other
objects. This “attention” angle is very small, normally, and the
duality of other images is automatically suppressed to conscious
vision although they are essential in the subconscious perception
of the stereo image, that is to the synthesis of the stereo image.
Outside this minute angle of acute vision, visual perception ex-
tends rather widely and eventually falls off. The sharpest cutoff
we have is the diffused image of the brows and the bridge of the
nose and the outer eyelids.
In the camera we have the sharp cutoff of the edge of the
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