APPENDIX B 319
Chain stereoscope.-A cabinet stereoscope
with the views hung in chains which pass
over twin sprockets thus bringing into
view one stereogram after another. More
familiar in Europe than here.
Chromatic perspective.-See Stereo-chro-
matism.
Chromatic relief.-See Stereo-chromatism.
Color correction.-The use of faintly tint-
ed filters with color film to compensate
for off standard color of incident light.
More important in stereo than planar
photography as normal color is an im-
portant factor in panortho stereo. Also
used to adapt color film to a type of light
for which it is not designed as the con-
version filter to use Type A kodachrome
with daylight. Also color control.
C. C. Filter.-One type of filter used in
color control. Also L. C. filters.
Color meter.-A special meter which indi-
cates the spectral balance of an existing
light of photographic level, and by doing
so indirectly indicates the proper correct-
ing filter which should be used. Among
the most popular are the H&H attach-
ment which converts the G.E. exposure
meter into a color meter and the Rebi-
koff precision color temperature meter,
made in Switzerland.
Color perspective.-See Stereo-chromatism.
Complementary stereoscope.-A stereo-
scope matched to the camera as is essen-
tial in orthostereoscopy.
Compressor, image.-A cylindrical lens
used in making stereo motion pictures to
permit a rectangular screen image instead
of the narrow vertical format of a half
frame.
Contour reversal.-A type of space con-
trol in which certain elements of the scene
are shown in pseudoscopic relief while
others are shown in proper stereoscopic
relief, although both elements are com-
bined in a single stereogram.
Convergence.-The meeting of visual (or
other optical) axes when produced from
two separate stations to a common object.
Absolute convergence is the actual angle
between the convergent axes and is identi-
cal with the parallactic angle. Relative
convergence is the convergence upon one
object within a scene compared with that
upon another object. Relative convergence
is the more important in stereo photogra-
phy. Convergence is often said to be the
primary stereo stimulus, but this has been
disproved.
Convergence camera.-A method of mak-
ing stereograms by altering the direction
of the camera between exposures so the
object is centered in both films. Impracti-
cal for any subject except one limited
largely to one plane. Otherwise more or
less serious distortion is introduced.
Conversion filter.-A specific type of color
control filter designed to ermit the use
of artificial light film by Baylight or vice
versa.
Coronet (Trade name).-An inexpensive
stereo camera and viewer using 828 or
equivalent size film. Comparable to a de-
luxe box camera.
Deuiation calculator.-Dial calculator for
determination of the range of deviation
in any scene before photographing.
Diagnostic stereo.-The use of stereograms
to aid in the diagnosis of visual disorders.
Diopter.-Ophthalmic lenses (and viewer
lenses) are designated by power rather
than focal length. The power in diopters
is equal to 100 divided by the focal length
in cm. Thus a zocm lens is five diopter, a
iocm is ten diopter, a 5cm is zo diopter
and so on.
Diplopia (Double vision).-Ordinarily an
abnormal visual condition, but normal to
all stereo vision outside the macular area.
Drawing, stereo.-A drawing made in
duplicate but with stereo differentiation
so that when viewed stereoscopically it
will have stereo relief.
Equivalent distance.-In stereomicrogra-
phy, a photograph made at a very short
distance is viewed as if it were at some
greater arbitrary distance, usually “read-
ing” distance. This apparent distance is
the equivalent distance. Also applied to
other distortions, deliberate and acci-
dental, of stereo relief.
False stereogram.-(See Spreader, Twister,
Infusible.) A true stereo air so mounted
that viewing is uncomkrtable or im-
possible.
Flicker projection.-Stereo projection in
which the two images are projected upon
a screen in rapid alternation, and viewed
through a shutter which alternately ob-
scures the right and left eyes in synchro-
nism with the projector.
Frame masking.-Masking the top and
bottom of the aperture in a motion plc-
ture camera (less commonly in the pro-
jector), to produce the desired square
stereo screen format.
Free vision.-Any system which permits a
true stereoscopic effect to be seen without
the use of any kind of viewer.
Fusion.-The visual registration of the
two images in the eyes. This is distinct
from the phenomenon of subjective sy”-
thesis to which the term is often applied.