320 THREE-DIMENSIONAL PHOTOGRAPHY
Purely a physioneurological factor.
Ghost image.-Any visual or photographic
image which permits objects behind it to
be seen: a transparent image. The condi-
tion common to images of objects not the
subject of direct vision.
Glyphoscope (Trade name).-A simple de-
vice now obsolete, used as both camera
and viewer.
Graflex (Trade name).-The stereo-gra-
flex uses 5x7 sensitive material to make
stereo pairs 31/2x5. Has stereo viewer
lenses in focusing hood.
Grid stereo.-Narrow strip elements from
two images alternate. Viewed through a
grid spaced before the print, the two eyes
see different images due to angular vision
through the grid. The least satisfactory of
the general integrated type of free vision
s tereogram.
Guildmount.-A special, rigid, cardboard
stereo mount made for the Stereo Guild.
HomoZogue.-That which exactly corre-
sponds in position, proportion or struc-
ture, In stereo applied to corresponding
points or parts in the two images.
Homologous distance.-The distance be-
tween two homologous points. Identical
with base or separation when the homolo-
gous points lie at infinity.
Homologous points.-The two point im-
ages in the stereo pair which exactly cor-
respond. The two images of the same nail-
head in a board, for example, are practic-
ally homologous points.
Hyperstereo.-Stereo with an extended
base. Results in theoretical error which is
practically imperceptible. Reduces appar-
ent distance of objects, which appear as
scale models of the larger object.
Hypostereo.-Stereo with diminished base.
Used for close-up and stereomicrography.
I1oca.-Stereo version of the 35mm Iloca
camera.
Infusible stereogram.-A stereogram so
made or so mounted that it cannot be
fused.
Integrated stereogram-A free vision ster-
eograin of the basic grid type but oper-
ating upon different optical principles to
provide stereo vision from integrated ele-
ments of the two images. A lenticular
(spherical or cylindrical) screen replaces
the grid. Peristereoscopy.
Interocular.-Basically the distance be-
tween the two eyes; also applied to the
separation of camera or viewer lenses. May
be variable,
Inversion.-The complete reversal of posi-
tion exhibited in the stereo negative as
compared with the true positions. The
optical phenomenon which makes neces-
sary the transposition of stereo prints.
Kelvin meter.-Color temperature meter.
See Color meter.
Lens, stereo-prismatic. -Su pplemen tar y
lenses for stereo close-ups which combine
both the positive refraction of the conven-
tional close-up lens and a prismatic devi-
ation which permits the image of the
close-up object to be centered in the filili
area.
Light control.-See Color control,
Macular vision.-That part of vision which
is characterized by maximum definition
and resolution. Also known as “sharp”
vision. The object of macular vision is
that object upon which the visual atten-
tion is fixed.
Magnification of viewer.-In orthostereo
the magnification is unity, as the taking
and viewing lenses compensate. A viewer
with lenses of less than the camera focal
length results in undesirable magnification
of the image. Magnification as a primary
function of the kiewer may be ignored
when the viewer is a complementary one.
MetastereoscoPy.-Reproduction of original
in normal proportions but in abnormal
size. Common in stereomicrography.
Mexican [email protected] stereoscope.
Mirror stereoscope.-A stereoscope which
involves reflection from a mirror. The
Wheatstone stereoscope largely used in
X-ray work is one type. See Reflecting
stereoscope.
Monocular viewer.-This is not a stereo-
scope. It is a sin le lens which is used to
give to a single p8otograph a three-dimen-
sional but not stereoscopic appearance.
Pantoscope.
Normal stereoscope.-A n y stereoscope
which uses stereograms whose infinity-
homologous distance is substantially equal
to the average interpupillary separation,
i.e. 65mm. Contrasted with the Brewster
in which the I-H points are much farther
apart than the normal human eyes.
Orthostereoscopy .-Tha t type of s term-
scopy in which the image is reproduced
in full natural size as seen at full natural
distance and in full normal degree of re-
lief. Not possible with projection nor free
vision: only I+ hen an individual viewer is
used, and this must be complementary to
the camera.
Panortho-stereosco&.-The neai est ap-
proach to perfection in stereo. This is an
orthostereogram in which full advantage
has been taken of the auxiliaries (q.v.),