CLOSE-UP STEREOGRAPHY 247
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SPLITTER MIRROR 5Or50 DOUBLE DIAGONAL
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- The beam splitter is used with two cameras in macro work when the
base is very small. The setting here is zero base.
- For greater stereo bases the 50-50 mirror permits one camera to be
moved sidewise to adjust base. Drawing shows zero base.
- When small bases are not required, the double diagonal pictured
here is easily operated and gives excellent results. The base is changed
by moving one camera away from the other.
6. When the camera is used with convergent rays (objects centered), the
actual relationship is that shown above. Camera is moved from C to C’
between exposures; object at 0.
7. A conventional “dark field” diaphragm used in microscopy.
- A stereo darkfield diaphragm corresponding to Fig. 7, but as
used for stereomicrography.
- A brightfield diaphragm, complementary to that of Fig. 8.
cameras receive a reflected image. However the smallest base is
one which is about^50 percent greater than the lens aperture, the
exact amount depending upon the lens mounting, the angle of
field and so on.
The lens mounts make it impossible for the lenses to work in
approximate contact with the prism, so relatively long focus
lenses are necessary to increase working distances, This, in turn,
indicates long bellows. The method is most easily applicable to
moderate degrees of macro, that is to a size ratio of about 1: 1.
For enlargements up to about 2: 1, the double diagonal may be
used with small lenses and small prisms, but for extreme work the
