Handbook of High Speed Photography - IET Labs, Inc.

At extremely short camera-subject distances, the camera lens
must be moved away from the film plane in order to bring the subject
into focus. This decreases the amount of light reaching the film, and
the lens aperture setting must be adjusted to compensate for this loss.
The curve in Figure 4-5 provides a straightforward means for determing
the amount of adjustment required for either a given bellows extension
or a given image magnification.
IMAGE SIZE
IMAGE MAGNIFICATION <
OBJECT SIZE
I 2 4 6 B 10 15
J I I I I I I I I
4 6 B
n—i—i—Tr
io 12 16 20
BELLOWS
EXTENSION
HKS..I0
Indicated aperture = K x effective aperture
„ ,. „ . „ Lens-to-film plane distance in inches
Bellows extension - 25.4 X Focal length of camera lens in millimeters
Figure 4-5. When camera is located close to the subject, multiplier
factor for determining indicated aperture (correct lens f/number setting)
from effective aperture (calculated from guide number data).
4.5 LIGHTING TECHNIQUES.
Many times objects to be photographed at high speed do not con
trast well with their backgrounds, and it is difficult to achieve clear,
high-definition pictures of them. This difficulty is augmented by the
usual absence of auxiliary light sources. Often this situation can be
greatly improved simply by either a light or a dark background behind
the subject. If several objects or moving parts are being studied simul
taneously, different colors or shades of paint can be used to improve
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