GLOSSARY
ABERRATION
­A defect in the formation of an optical
image; for example, astigmatism, chromatic
aberration, curvature of field, and so forth.
ABSOLUTE TEMPERATURE
­The temperature
measured from absolute zero. Expressed as degrees
Kelvin (°K) in the Centigrade system where
absolute zero is ­273°C or in degrees Rankine in
the Fahrenheit system where absolute zero is
­459°F on the scale.
ACCELERATOR
­Chemical constituent of photo­
graphic developers that activates the developing
agent and swells the gelatin to hasten penetration of
the solution. See SODIUM HYDROXIDE,
SODIUM CARBONATE, SODIUM META­
BORATE, and SODIUM BORATE.
ACHROMATIC COLORS
­Colors perceived as
having no hue (white, black, gray, and silver).
ACHROMATISM
­The absence of chromatic
aberration.
ACID, ACETIC
­A colorless liquid of pungent odor
used in stop baths and in fixing baths. In
concentrated form it attacks the skin and produces
painful blisters. A concentrated solution of 99%
solidifies at 62°F and forms a mass resembling ice
(Glacial Acetic­Acid).
ACID, BORIC (BORACIC ACID) H
3
BO
3
­
Colorless, odorless, transparent crystals, or a white
amorphous powder. Slightly soluble in water and
more soluble in glycerine and alcohol. Used in
toning and fixing baths.
ACID, SULFURIC, H
2
SO
4
­ syrupy, odorless liquid,
colorless or slightly yellow. Used for preparing a
tray­cleaning solution and in fixing and reducing
solutions.
ACTION
­Movement within a scene being photo­
graphed. Also, the picture portion of a motion
picture as differentiated from the sound track
portion.
ACUTANCE
­An objective measure of the ability of a
photographic material to show a sharp line of
demarcation between contiguous areas receiving
low and high exposures. It correlates well with
subjective judgments of picture sharpness. It is the
mean of the square of the density gradients times the
density scale over a boundary.
ADDITIVE PROCESS
­Any color process in which a
reproduction is formed by a combination of images
each of which supplies color in proportion to the
color observed in the original scene. In a typical,
three­color additive process, the colors of the
images are blue, green, and red. See SUB­
TRACTIVE PROCESS.
AGC
­Automatic gain control. Regulates the volume of
the audio or video light levels automatically within
a camcorder.
AGITATION
­The act of moving a photographic film,
plate, or paper in a processing bath or moving the
bath relative to the photographic material during
processing.
AIR BELLS
­( 1) Air bells are bubbles of air that prevent
contact between a processing bath and localized
areas on the surface of a photographic material.
(ASA) (2) Undeveloped spots on negatives or
prints caused by air bubbles, preventing access of
developer.
ALKALI
­A water soluble compound capable of
uniting with and neutralizing acids. The alkalies
commonly used for photographic processing baths
are sodium hydroxide, potassium hydroxide,
sodium carbonate (monohydrate and anhydrous),
potassium carbonate, sodium tetraborate, sodium
metaborate, and ammonium hydroxide.
AMBIENT SOUND
­Background sound or wild
sound. Sound that surrounds the scene or location,
received by the microphone and recorded onto
magnetic tape.
AMMONIUM THIOSULFATE, (NH
4
)
2
S
2
O
3
­A
white salt freely soluble in water. Used in the
preparation of rapid­fixing solutions.
ANALOG
­An analog signal that fluctuates exactly like
the original stimulus (for example, sweep
second­hand clock, phonograph player).
AI-1

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