Section 2 Shooting
288
Copyright Goodheart-Willcox Co., Inc.
A reproduction ratio of 1:1 (life-size, or a
magnification rate of 1×) is generally considered
the borderline between the close-up range and
the macro photo range. In the macro range,
various types of accessories are used to increase
the magnifying power of the camera’s lens.
At approximately 25×, another borderline
is passed, moving into the third range of
magnification. This is the highly specialized realm
of photomicrography, in which a microscope is
used to achieve extremely high magnifications.
Ways of Getting Close
In the close-up range (up to life-size), macro
lenses provide the advantage of simplicity and
ease of use. These lenses also are versatile, since
they can be used for normal photography as well
as close-focusing situations.
For magnifications greater than life-size,
other devices must be used in combination with
the camera lens. The devices and methods used to
obtain greater magnification include the following:
• Close-up diopters. These magnifying devices
screw onto the front of the camera lens. In
effect, they shorten the focal length of the lens
and thus increase the image size on the film.
Usually sold in sets of three, they can be used
singly or in combination. See Figure 12-57.
These simple single-element lenses can
degrade optical quality. The optically superior
two-element diopters made by several camera
manufacturers provide much sharper images.
They can be used with any brand of lens with
the appropriate filter size.
• Extension tubes. Much higher
magnifications can be achieved by inserting
an extension tube to move the lens farther
away from the film plane. Unlike the close-
up lenses that put additional optical elements
in the light path, the tubes add only distance.
The tubes come in various lengths and
are sometimes sold in sets, Figure 12-58.
Tubes of different lengths can be coupled
together to achieve the desired extension.
To determine the extension needed for a
desired magnification, multiply the focal
length of the lens by the magnification.
With the lens focused at infinity, adding
an amount of extension equal to the focal
length will produce a 1:1 reproduction ratio.
Thus, to achieve a 3:1 ratio (3× magnification,
or three times life-size) with a 50 mm lens,
couple together tubes for a total extension of
150 mm, or about 6″.
• Bellows. In effect, the bellows is a variable-
length extension tube, with the camera
attached to one end and a lens to the other.
Due to its bulk and the fragility of the
folding bellows material, this device is more
commonly used in studio work than in field
photography.
• Reversed lens. Mounting a lens backward,
using an accessory called a reversing ring, is
one of the most effective methods of gaining
higher magnifications. See Figure 12-59.
Goodheart-Willcox Publisher
Figure 12-57. A set of close-up diopters.
Porter’s Camera Store
Figure 12-58. Extension tubes increase magnification,
but do not degrade the image.