Advanced Photography Course

Figure 2-3.--How a sensitometer is used to produce sensitometric strips.

information should include the type of developer, the
development temperature, the development time (or
machine speed), the type of film, the agitation used,
and so forth.

ANALYZING CHARACTERISTIC
CURVES

By analyzing a characteristic curve, you can

determine the effective speed of the emulsion, the
contrast, the latitude, and the useful exposure range.
Figure 2-6 at the end of the chapter shows
a typical characteristic curve with the various parts
and their names. Refer to figure 2-6 frequently

as you proceed through this chapter.

The speed of the material being evaluated

determines the position of the curve regarding log
exposure (log H) or horizontal axis. The length and
slope of the straight-line section are the main
variations to the shape of the curve. All densities on
the straight-line section of the D-log H curve increase
proportionally with an increase in development time.
The slope or gradient of the straight-line section of the
curve also increases, as development is increased; that
is, it gets steeper.

Toe Section

The toe section (fig. 2-6) is a concave, rising

portion of the curve that gradually increases in

2-9

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Advanced Photography Course

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