COUPLERChemical compound in color developer
that can react with the oxidized developing agent in
the sensitized material to form a dye color.
CRITICAL FOCUSThat point of focus at which
resolution is at its maximum. (NMA)
CROPTo trim or cut off parts of the picture by printing
methods to eliminate superfluous portions, and thus
improve the composition.
CROP MARKSMarkings placed on original copy,
indicating where part of the top, bottom, or sides of
the picture are to be omitted.
CURVATURE OF FIELDAn aberration of a lens that
causes the image of a plane to be focused into a
curved surface instead of into a plane.
CUTAWAYS (MOTION PICTURE)Shots of related
and previously established outside interest used to
divert the audience attention in order to cover jumps
in action, screen-direction changes, and passage of
D-LOG E CURVESee CHARACTERISTIC CURVE.
DARK SLIDEThe opaque slide that covers the film
in a film holder, plate holder, film pack, or film
DARKROOM A room in which all light of color
quality not safe for undeveloped sensitized
materials has been excluded. It is used for loading
and unloading and the developing of exposed
photographic film or paper.
DENSITOMETERDevice to measure the optical
density of an image or base by measuring the
amount of incident light reflected or transmitted.
DENSITY The light-absorbing quality of a photo-
graphic image is usually expressed as the logarithm
of the opacity. Several specific types of density
values for a photograph may be expressed; however
diffuse transmission density is one of the most
important for photographic transparency materials,
such as negatives. Diffuse reflection density is
generally of interest for photographic prints.
DEPTHIn a nonstereoscopic picture, an illusion of
three-dimensional space that is sometimes created
by a combination of favorable lighting and coloring
of the set and favorable viewing conditions for the
DEPTH OF FIELDThe distance between the points
nearest and farthest from the camera that are
acceptably sharp at a given lens setting.
DEPTH OF FOCUSThe allowable error in lens-
to-film distance within which an acceptably sharp
image of the subject focused upon will still be
DEVELOPER (CHEMICAL)A chemical reagent
used to produce a visible image on an exposed
DEVELOPER, COLORA photographic developing
solution capable of reducing silver halides with the
simultaneous production of an insoluble colored
oxidation product in the regions where silver is
DEVELOPING AGENTChemicals used in the
photographic processing baths to convert the latent
image into a visible and photographically useful
DIAPHRAGM A device, such as a perforated plate or
an iris, that limits either the aperture of the lens, the
field covered by the lens, or both, depending upon
DICHROIC FOGA deposit of colloidal silver on a
photographic film caused by improper processing.
This deposit commonly appears red by transmitted
light and greenish by reflected light.
DIFFRACTION (OPTICS)The bending of light
waves around the edges of opaque objects.
DIFFUSERDevice for obtaining diffuse direct
illumination, such as a wire screen, piece of cloth,
or translucent membrane, placed between a light
source and the subject illuminated.
DIFFUSION (l) (Optical) The scattering of light rays
so as to cause the light falling on a surface or passing
through an aperture to be coming from all directions
in contrast to the regular radiation of light from a
point source. Diffusion may be introduced by
reflection from a matte surface, by transmission
through a frosted or opal glass, or by the use of an
integrating bar. When diffusion is complete, a sharp
image of the light source can no longer be seen, and
its place is taken by a uniform, extended source that
emits light equally in all directions. (2) (Chemical)
The migration of molecules or ions in a solution
tending to reduce a difference in concentration
between two adjacent regions.