U
Model 196A Section 111
Paragraphs 3-20 to 3-31
e. Calculate total sweep time by multiplying sweep This distance will differ somewhat from oscilloscope
length in cm times sweep speed in sec/cm. Multiply to oscilloscope and from top to bottom of the graticule.
the answer by 5 and this will. be the minimum ideal Good practice is to take a few trial exposures to de-
shutter speed when no drift or jitter is present. termine the exact amount of parallax and then keep a
record of it for future reference. Refer to paragraph
f. Find the basic aperture/shutter speed point in 5-5 for a complete description of parallax problems.
figure 3-3. Now go up or down that diagonal line until
it intersects with the shutter speed closest to that NOTE
found in step e. Follow the horizontal line at that in-
Parallaxwillcause some error in scale mea-
tersection to find the new aperture setting.
surements when the graticule is used as a
reference. For maximum accuracy, make
3-20. INTENSITY SETTINGS.
measurements near the picture center.
3-21. Position your head against the 196A viewing
port when making oscilloscope intensity and focus
3-26. FILM DEVELOPING.
settings. A small change in intensity barely percep-
tible tothe eye willproduce the same result as changing 3-27. Developing time depends on the ambient tem-
the aperture settings two f/numbers. The intensity perature and the film type being used. Ikveloping
should be set so that no general glow or blooming is time for Polaroid@ type 42 and 47 film is 10 seconds
seen on the cathode ray tube. If this rule is followed, at room temperature. For type 46L, the film should
the data given in table 3-1 and figure 3-3 will prove be developed for 2 minutes. In general, developing
of great he4 in the saving of film and time. There for longer periods will increase contrast, but will
are specialized situations, of course, when details in also tend to render very faint traces invisible. When
fast rise times, etc., will want to be observed. In developing pictures at cooler temperatures (below
these cases, the intensity will have to be set some- 720F), increase developing time. The ideal time will
what higher. have to be determined experimentally. However, for
type 47 film at temperatures around 3WF, a develop-
3-22. GRATICULE EXPOSURE ing time of 40 seconds is a recommended starting point.
See figure 3-4 for instructions on film developing.
3-23. In some oscilloscopes, when using normal trace
and graticule intensity, it will not be possible to il-
NOTE
luminate the graticule enough to produce a satisfactory
picture of both the trace and the graticule together. 1) Polaroid prints made with type 42 and 47
If you have this problem, there are two possible solu- film should be coated as soon as possible after
tions: exposure with the print coater supplied with
each roll of film.
a. Reduce the trace intensity and increase the
exposure time (decrease shutter speed), leavingthe 2) Transparencies made with type 46L film
graticule fully illuminated. should be hardened after ewosure in the #646
Dippit which is purchased separately. For
b. Using the exposure recommended in paragraph good results, follow carefully all directions
3-19, take the picture of the trace with the graticule supplied with the film roll and the Dippit.
turned off. Then turn the trace intensity off and set
the f/number between f/5.6 and f/16 (depending on 3-28. SCALE MEASUREMENTS.
graticule brilliance). Turn the graticule on, and expose
3-29. Scale measurements on the print demand extra
it for about 5 seconds. This procedure is also recom-
care during exposure and development in order to ob-
mended for long sweep speeds (above 5 seconds),
tain maximum accuracy. Whenever possible, use
where exposure of the graticule during sweep time
reduced aperture size and long exposure to effect the
would cause excessive graticule exposure.
sharp, thin line trace desirable. When making scale
measurements using the graticule as a reference, keep
NOTE
in mind the limitations caused by the effects of parallax
When an f/number below f/5.6 is used, the between the graticule and the oscilloscope trace. These
graticule should always be exposed separately effects can be minimized by making the scale measure-
as in part b above. ments near the center of the oscilloscope presentation
(see paragraph 5-5).
3-24. PARALLAX .
3-30. MULTIPLE EXPOSURES.
3-25. Due to the fact that the oscilloscope graticule
lines are separated somewhat from the cathode ray 3-31. Multiple eqosures are often desirable to either
tube phosphor, and the fact that the oscilloscope view- compare signals that differ slightly during adjustments,
ing angle differs from the lens angle, some parallax etc. , or as a measure to conserve film when attempt-
will exist. If it is necessary to have the trace posi- ing to determine correct exposure for specialized con-
tioned vertically in a particular area on the graticule ditions. The multiple picture knob (figure 3- 1, sheet 2)
(for making convenient scale measurements, etc.), the moves the lens in relation to the camera back 1/2 cm
viewed trace will have to be offset. In most oscillo- for each of its 11 detented positions. The knob should
scopes, this distance is from 0.1 to 0.2 cm, that be in the CTR position when the graticule is to be ex-
is, the viewed trace should be set 0.1 to 0.2 cm higher posed. The graticule should be exposed only once dur-
when viewed than it is desired on the finished print. ing multiple exposures as explained in paragraph 3-22.
3-7
01038-1 |
ACEC
