354 THE HASSELBLAD MANUAL
depth-of-fi eld and exposure. The most practical way to determine magnifi cation is to relate
the size of the area covered to the size of the same area as seen on the focusing screen. With
fi lm, the latter is the full focusing screen area in H or V system cameras. In digital imaging, you
must consider the masked down area that corresponds to the sensor size. In all cases mag-
nifi cation is the size relationship of the two. If you cover an area 110 147 mm on the 36.7
49.0 sensor, you have a 0.3 magnifi cation. The image is one-third the size of the actual
subject. Covering an area 367 367 mm on the 36.7 36.7 sensor means a magnifi cation of
0.1. If you cover a very small area of 16.5 22.1 mm on the 33.1 44.2 sensor, you double
the size of the subject and have a 2 magnifi cation.
Life-Size Magnifi cation
Life-size magnifi cation refers to recording a subject in the camera in its actual size, which
means that the subject size is determined by the size of the sensor or fi lm format in the cam-
era. We have life-size magnifi cation when a subject 36.7 49.0 mm is photographed with a
36.7 49.0 sensor. A smaller subject of 33.1 44.2 mm produces life-size magnifi cation on
the smaller 33.1 44.2 sensor.
Life-size magnifi cation for the fi lm format is obtained on the HC Macro 120 by setting the
focusing ring at its maximum extension. With other lenses you always achieve life-size magni-
fi cation when you add extension tubes that are equal in length to the focal length of the lens
or close to the focal length; for example, 78 mm (H52 and H26 tubes combined) for an 80 mm
lens. In life-size magnifi cation, the subject distance is equal to the image distance with the total
distance between subject and image plane 4 the focal length of the lens. The necessary expo-
sure increase is 2 f stops, and the total depth-of-fi eld at f/11 is about 2 mm (see Figure 19-2).
Figure 19-2 Life-size magnifi cation. Life-size (1:1) magnifi cation with extension tubes is obtained
when the length of the extension tube or tubes (L) is equal to the focal length (F) of the lens
(L F). The distance from the subject to the image plane (D) is equal to 4 the focal length
(D 4 F). The exposure increase (E) is always 2 f stops, and the depth-of-fi eld at f/11 is
about 2 mm. Life-size magnifi cation can be obtained with the HC Macro 120 mm lens in the H
system without any close-up accessories.
Depth-of-Field
As in long distance photography, depth-of-fi eld is determined mainly by the lens aperture.
Magnifi cation is however also a determining factor in close-up work. Close-up photography
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