The DARKROOM COOKBOOK, Third Edition

34 THE DARKROOM COOKBOOK
A
B
C
D
Defi nitions
The Anatomy of Film
A. Protective coating, dissolved during development.
B. Emulsion, light-sensitive silver bromide crystals suspended in gelatin. The size of the crystals (granules)
controls speed, grain, contrast, and resolution. All can be altered to some extent in the development process.
C. Base, usually some form of pliable, clear acetate.
D. Antihalation backing, which absorbs excess light that penetrates the
emulsion and base and prevents it from bouncing back and scattering in the
emulsion, thereby fogging and degrading the image. Also dissolved during
development.
● Acutance: The separation of adjoining objects or details on a fi lm. Also known as
sharpness of defi nition and edge sharpness. When two objects are adjoining on
a fi lm, acutance describes how sharp and clear the line is between them. All the
things that cause graininess can lower the acutance of a fi lm. In addition, halation
(see antihalation backing, above), irradiation (the spreading of light as it passes
through the emulsion), and grain size affect acutance.
Slow, thin emulsion fi lms, such as Kodak Technical Pan or Ilford Pan-F, developed
in high-defi nition developers such as Windisch Extreme Compensating Developer
or POTA, will produce negatives, even from 35 mm, of extremely high acutance
with the ability to enlarge to mural size. The trade-off is an extremely low EI.
● Grain or Granularity: The measurable grain size of any undeveloped fi lm. Generally,
slower fi lms have smaller grain, faster fi lms have larger grain. Grain size is predetermined
by the manufacturer.
● Graininess (grain aggregation): The clumping together of individual grain particles
during development. Graininess can be induced by exposure to excessive
heat before or after exposure (graininess does not change after development is
complete). The choice of developer can reduce or increase graininess. It does not
affect grain size.
Factors that can increase graininess are over-vigorous agitation during development
with old-style emulsions, solutions that vary more than �2 degrees, storage
at high temperature; and overexposure in the camera.