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Operating Instructions—C-30B Camera
PICTURE TAKING
Photographing Repetitive Signals
The following procedure can be used as a guide to obtain
an exposure o f a repetitive signal trace:
1. Position the external graticule, if the instrument crt
has one, fo r the white lines.
2. Mount the camera on the instrument w ith the proper
camera adapter.
3. Obtain the signal and adjust the Controls fo r the
desired display.
4. Attach the camera to the adapter and secure the
camera against the instrument.
5. Adjust instrument focus, astigmatism, and intensity
Controls to obtain a sharp trace.
6. Set the f-STOP selector fo r the largest lens opening
(smallest f-STOP number) and carefully focus the
camera.
NOTE
When using an instrument with an external graticule,
focus the camera halfway between the trace and the
external graticule and set the aperture to the highest
f-number that w ill s till allow adequate film exposure.
7. Set the instrument intensity control between one-
third and one-half clockwise, Scale Illum ination
three-quarters clockwise, camera SPEED selector to
1/30, and f-STOP selector to f/5.6. The above control
settings should be reasonably close for most film
around 200 ASA and a waveform w ith a frequency
near 1 kHz. For film with a 3000 ASA rating and a
waveform w ith a frequency near 1 kHz, use a SPEED
selector setting of 1/4 and an f-STOP selector setting
o f f/5.6.
Photographing Single-Sweep Displays
Single-sweep displays are formed when the oscilloscope
spot sweeps across the screen only once. The actual ex
posure time is thus determined not by the shutter speed
setting, but by the duration of the sweep plus phosphor
persistence, provided the shutter is open sufficiently long.
In one type of single-sweep photography, the graticule
exposes the film fo r the time set by the shutter, while the
spot on the screen exposes the film for only the duration of
the sweep. It is therefore not usually possible to adjust both
the trace and graticule for the same intensity and still
obtain good pictures, since the effective exposure tim esfo r
the two are different.
Success in obtaining good photographs o f single-sweep
displays w ill come with experience. A few tips, however,
may reduce the need fo r experimenting.
1. Use
steps
1
through 6, under Photographing
Repetititve Signals, to set up the camera.
2. Select a shutter speed which keeps the shutter open
longer than the time o f the event to be photographed
(at least 10 seconds).
3. Use the highest practical intensity w ithout causing
defocusing of the trace. Photograph fast areas of a
display at the center of the crt to make use of the
light transmission characteristics of the lens. This
prevents many defocusing Problems caused by high
intensity settings.
4. Where practical use an f-STOP setting higher than f/4
if an external graticule is used. This permits both the
trace and the external graticule to be in focus.
5. Since the shutter speed has already been determined,
the quality of the photographic reproduction w ill
depend largely on the selection of lens opening. In
single-sweep applications make camera settings for
the trace intensity and duration; graticule Illum in
ation cannot be used as a reference.
PICTURE TROUBLE
Wide Trace
If the trace is too wide on the picture (defocused due to
high light intensity), use either a higher f-STOP setting or a
faster shutter speed. If the defocused trace cannot be
improved by using either a higher f-STOP setting or a faster
shutter speed, refocus the camera.
No Image on Picture
1. Use higher intensity and scale illumination settings.
2. Use a slower SPEED selector setting.
3. Set the f-STOP selector to a smaller number.
4. Leave the shutter open fo r 10 seconds after trace
occurs so that all possible display light w ill be
integrated (Single-Sweep Applications).
5. Use a film with a higher ASA rating.
6. Prefogging or postfogging may help. Refer to Helpful
Techniques w ith Film (Single-Sweep Applications).
7. If Polaroid film is being used,try underdeveloping it;
i.e., remove the print before fu ll development time
has expired (Single Sweep Applications).
@
2-15
Summary of Contents for C-30B
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