larger crystals more easily capture the few rays of
light in a dark environment. When the fast film is
developed, its larger crystals yield larger bits of sil-
ver. The advantage is that the film needs less light
to form an image. The potential disadvantage is
that these larger crystals in very fast films repro-
duce what should be uniform gray areas—not as
smooth tones—but with distinctly visible specks or
grain.
In general, each increase in speed also increases
graininess. If maximum sharpness and minimum
graininess are your desire, select slower rather than
faster films.
Some newer films have reduced graininess. Recent
advances in technology have changed what used to
be a fairly direct relationship between film speed
and grain. The silver halide crystals in T-grain or
core-shell emulsions, such as in Kodak’s Max or
Ilford Delta films, have a flattened surface that
exposes more of each crystal to light. The result is
film with significantly reduced grain for its speed.38 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY
On some films, you
might see the European
DIN (Deutsche Industrie Norm)
rating; for example, ISO 200/24.
The DIN rating adds 3 to the rat-
ing each time the film speed dou-
bles. DIN 24 (equivalent to ISO
200) is twice as fast as DIN 21,
half as fast as DIN 27. Except for
the unlikely case of using a piece
of equipment marked only with
DIN numbers, you can ignore the
DIN part of an ISO rating.FIGURE 3.3
The photo on
the left was
taken with film
camera using
ISO 800 speed
film. The photo
on the right was
taken in low
light with a dig-
ital camera at
ISO 400.Other factors also affect grain. Graininess is more obvious in areas of uniform tone—
such as the sky—than it is in textured areas. Also, graininess becomes more apparent
the more a picture is enlarged. That is why a print from a 35mm negative usually
looks grainier than the same size print from a larger negative. Grain is also affected