Lens
Gom
pati
bi
I iU-continued
''
Focal Length
Conversion
The frame size of conventional
135 film is
24
x
36mm, and an
1X240 film frame measures
16.7 x
30.2mm.
Because 1X240 film differs in size from 135 film, images obtained using the
same lens will also differ.
Diaoonal line
lmage area of 1X240 film
(16.7
x
30.2mm)
Picture
angle of
135 film
Picture anole of 1X240 film
.
The
size of one
lX24O film frame is
approximately 0.8
times that of conventional 135 film in
diagonal
line. Therefore, the focal length of 135 format x 0.8 is equal to the focal length of
the
1X240 format, and focal length of lX24O format x 1 .25
is
equal
to
the
focal length
of
the 135
format,
yielding
the same
picture
angle.
.
The following table shows the approximate focal length of the 1X240 and 135 formats:
{mm)
1X240
(H
type)
19 20 22 24 28
30
40 48
56 60 68
70
84
108144160180
135 24 25 28 30
?6
)7.! 50 60 70 85 37.4105135180200 225
lmage area of 135 film
(24
x 36mm)
36
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