Hasselblad Digital Camera, Руководство пользователя

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THE HASSELBLAD MANUAL
Image Quality with Zoom Lenses
When designing a fi xed focal length lens, the lens designer only needs to be concerned about
the lens performance at one specifi c focal length. In a zoom lens, the optical technician needs
to worry about the quality at every focal length and there has to be a compromise. Having
identical quality at every setting within the zoom range can only be a dream. The best that
a lens designer can do is come up with a lens design that produces completely acceptable
sharpness at all focal lengths, and the Hasselblad lens designers accomplished this beauti-
fully. MTF diagrams for zoom lenses usually show the curves at two or three different focal
length settings. The MTF diagrams for the HC 50–110 zoom lens are shown in Figure 14-5
Figure 14-4
MTF diagram. MTF diagrams for the HC 3.2/150 mm wide open at f /3.2 and closed
down to f /8 (top) and for the HC 4/210 mm wide open at f /4 and at f /8 (bottom).
0
20
40
60
80
100
0 10 20 30
Image height (mm)
MTF (%)
f/3.2
0
20
40
60
80
100
0 10 20 30
Image height (mm)
MTF (%)
f/8
0
20
40
60
80
100
0 10 20 30
Image height (mm)
MTF (%)
f/4
0
20
40
60
80
100
0 10 20 30
Image height (mm)
MTF (%)
f/8