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4.5.2. Exposure time
20
The correct exposure of a film depends on several factors: the camera, the film type, the
exposure time, the aperture, the illumination of the object and also the magnification
factor i.e. the area on the film which is used to record a given area of the object.
These are all important factors and a complete coverage is impossible here. However,
some examples are given in Table 4.1 below for a set of common conditions. Initial
attempts can be made by referring to the tabled data, and good results obtained after
taking a few trial photographs.
The film used in the example is a professional daylight film developed to either 800 or
1600
ASA.
However, other films may be used
as discussed
below.
The camera used
(Olympus
OM-2) had a 50 mm focal length f 3,5 lens. The camera used
with the operation microscope was a Zeiss camera with an f 14 aperture (determined by
the operation microscope).
A Zeiss operation microscope type OM-1 was fitteded with B & K Flexible Light Cable
AE 6100 and Adaptor WA 0362. The gain setting was x6 and the exposure time as given
in the table below:
Film
Fixed light
Stroboscope
Photo
developed to
100 Hz
Flash
800 ASA
1/a
1/2
+
1600 ASA
1J15
1/4
++
T00363GBO
Table 4. 1. Exposure times. The
+
designation for photoflash {1/60 s
setting) indicates useful results
For still pictures a less sensitive film may be used by choosing longer exposure times.
Effective flash photography of the vocal cords would be doubtful using sensitivities of
400 ASA and less. A higher gain setting is not recommended. Enlargement of the photo-
graphs is preferable.
The other instruments used for photography were:
1. A Stortz "Hopkins" endoscope with detachable light cable
2. A Wolf "Von Stuckrad" endoscope with integral fibre cable
3. A Olympus fibrescope with a 3,7 mm diameter
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