ANGLE OF ACCEPTANCE–The angle that objects
must align within to affect the reading of a
photoelectric exposure meter.
ANGLE OF FIELD–A property of a lens. The angle
subtended by the lines that pass through the center
of the lens and locate the diameter of the maximum
image area within the specified definition of the
lens. Also called angular fields.
ANHYDROUS–Dry,
containing
no
water
of
crystallization.
ANTICURL BACKING–A transparent, gelatin
coating sometimes applied to the opposite side of a
photographic film from the emulsion to prevent
curling by balancing the forces that tend to curl the
film, as it is wet and dried during processing.
ANTIHALATION COATING–A light–absorbing
coating applied to the back side of the support of a
film or plate, or between the emulsion and the
support, to suppress halation (also called
antihalation backing). See HALATION.
ANTISLUDGE AGENT–A chemical compound
added to photographic processing solutions to
prevent the formation of sludge. Sodium
metaphosphate and boric acid are commonly used
for this purpose.
APERTURE–In an optical system, an opening through
which light can pass.
APERTURE, CURTAIN–The slit in a focal–plane
shutter that permits light to reach the film. The slit
size may be either fixed or variable.
ARTIFICIAL LIGHT–Illumination provided by
incandescent, fluorescent, or flame sources.
ASPECT RATIO–The ratio of the height to the width
of the film or television frame; that is, three units
high to four units wide (3:4).
ASTIGMATISM–A lens aberration that causes an
off–axis point to be imaged as a pair of lines at right
angles to each other and in different focal planes. A
lens having astigmatism is unable to image
horizontal and vertical lines in the same plane with
equal sharpness.
ATMOSPHERIC PERSPECTIVE–Applied to the
effect of distance created by atmospheric haze in a
photograph. It lightens the tones as the distance
increases.
AUDIO TRACK–The area of the videotape that is used
for recording audio information.
AUTO IRIS–An automatic control of the lens
diaphragm.
AUTOFOCUS–A feature of certain cameras or
enlargers by which the image is kept in focus
automatically regardless of the degree of reduction
or magnification.
AVOIRDUPOIS–The system of weights commonly
used in the United States and the British Empire in
which the primary unit is the pound (7,000 grains);
usually expressed in pounds, ounces, and binary
fractions thereof.
BACK LIGHT–Illumination from behind the subject
in a direction substantially parallel to a vertical
plane through the optical axis of the camera.
BACKGROUND –(1) That part of the landscape which
is more distant than the principal object from the
camera. (2) A screen, drape, or projected scene used
in a photography studio behind the subject.
BACKING PAPER (ROLL FILM)–The protective
strip of paper to which the film is attached. Backing
paper is usually black on one side and colored on
the opposite side. Numerals are usually printed on
the colored side in a position where they can be
viewed through the camera window. Also called
duplex paper. (ASA)
BARN DOOR–Folding wings used in front of studio
spotlights to aid in directing the light and to shade
portions of the subject from direct illumination.
BASE DENSITY–The density of a film base. No plastic
is 100% transparent, so all films have some base
density.
BATH–Any chemical solution used in processing
photographic materials.
BEAM SPLITTER–An optical system so arranged as
to reflect or transmit two or more portions of a light
beam along different optical paths.
BELLOWS–The extensible lightproof device that joins
the lens board to the film support section of a
camera
BLEACH, PHOTOGRAPHIC–(1) To remove an
image from a photographic film. Especially to do
this by converting a metallic silver image to a halide
or other salt that can be removed from the film with
hypo. When bleaching is not carried to completion,
it is called reducing. (2) Any chemical reagent that
can be used for bleaching. (3) Any chemical solution
used for bleaching.
AI-2
