LESSON 1
Paper emulsions are particularly thin to increase the reflectivity of the
finished print and to make it extremely flexible.
c. There are three types of printing paper emulsions: bromide,
chloride, and chlorobromide. The main difference among these types is speed
and latitude.
3. Development papers.
Development papers (photographic printing papers)
have a gelatin surface that contains light-sensitive silver halides.
Following exposure, the papers are subjected to a precise chemical
development process.
a. Chloride papers.
Chloride papers, have a slow speed emulsion and
contain silver chloride.
They have a fine grain and produce deep blacks.
Because of low sensitivity to light, they are used for contact printing.
Chloride papers are made in different contrasts, ranging from soft (low
contrast) to hard (high contrast).
b. Bromide papers. Bromide papers, which have a faster emulsion speed
than chloride papers, achieve sensitivity through the use of silver bromide
halides. They produce blacks that are warmer than those of chloride papers.
Because of the relatively high sensitivity to light, these emulsions are
particularly suitable for projection printing.
c. Chlorobromide papers. Chlorobromide paper emulsions, which contain
both silver chloride and silver bromide halides, produce pleasing warm
blacks.
Emulsion speed lies between that of chloride and bromide papers.
Chlorobromide papers are produced in a wide range of contrasts and are used
for both contact and projection printing. This type of paper is standard in
the Army.
4. Paper contrast.
Density can be referred to as the amount of metallic
silver deposited in any area of an emulsion.
The difference between the
densities of the various areas within the emulsion is called contrast.
Since a bright area of a subject reflects the greatest amount of light, it
is called the highlights. On the negative the highlight portion will have
the greatest density.
On the print it will have the least density,
therefore appearing as white. On the other hand, any portion of the scene
reflecting little or no light is called the shadow area. This portion of
the negative will appear dark or black. All the brightness values which lay
between these two extremes are called the middle tones and are represented
on the paper in varying shades of gray.
The difference in brightness
values, ranging from the highlights through the middle tones to the shadows
is called "subject contrast".
Normal contrast is represented by a full
range of densities.
High image contrast consists only of highlights and
shadow with little or no gradation of tones between them.
Low image
contrast has
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