Model 196A. Section IV
Paragraphs 4-1 to 4- 10
SECTION IV
PRINT EVALUATION
4-1. INTRODUCTION. &ev I LIGHT LEAKAGE. Light leakage is another
d of film fogging. Some common sources are
4-2. This section contains information for your use listed below.
in correcting any problems yau may have in oscillo-
scope photography. In each we, reference is made @ Improper mounting (paragraph 3-4) which does
to the particularparagraph ineectionm that will offer not permit the camera nose to seat tightly against the
more detailed instruction8 on how to prevent these graticule.
difficulties.
b. Stray light entering the edge of the graticule.
MaaWng the edge of the graticule with black tape will
usually solve this problem.
4-4. GENERAL. Fogging is the objectionable light
areg over either ,part of, or the whole print. Many E. Light entering the louvers of the oscilloscope
different factor6 can be respaneible for fogging, but a&@o the cathode ray tube to the phosphor. This
in most cases they can be corrected with Uttle diffi- is 'a'more difficult problem, and is probably best
culty. TWQ main causes are UBtedbelow. eolved by reducing the ambient light.
4-6. INTERNAL8WRCES. Most cases of toggiaS CAUTION
stem from the 0sciUomape ita&. These problems
If blacltcloth shielding is ever used, be care-
can become difficult to control when time mqxmres
ful not to cut off the air circulation to the
are necessary. &me of the most common faults are
oecilloscape.
given below.
a. Excessive Mlliance can cause a general bloom-
ing of the trace which ten& to light the entire scmen.
This can be easily corrected by lowering the oacillo=
e due to tearingis usually caused by
=aPe-w. ,
nat pullingthe negative tab straight while advancing the
film. The tab should always be pulled in a straight line
b. Low frequency light emitted from the cathode on
parallel with the long axis of the camera back. This
an un-aluminieed tube can cause considerable fag-
procedure, in addition to care in keeping the inside of
ging, especially on time expowrres. A blue filter
thecamera back clean will prevent most film damage.
placed either over the camera lens or on the graticule
will be of some help for this type of fogging.
L PROBLtMS.
c. An unblanked oscilloscope can cause tnnrble,
eapeciallyif it is being wed far recording transient6,
since the spat remaln6 visible until the trrrnsient oc- e 4-1 illustrates many of the problems
curs. This problem can be minimized by poeitioning commonly encountered in oscilloscope photography.
the spot to apoiat just undew the edge ofthe beeel, or Youwill probably find that by reading section III care-
if the bezel does aaL cover the ec@e of the cathode ray fully, many of these problems can be avoided with sub-
tube, the spot may be masked with a piece of tape. arequent saving of time and film.
Refer to
Picture Received Picture Desired Cause
Paragraph
Camera nose not mounted 3-4
against the graticule.
Note fogging and reduced
graticule size.
d
01 038- 1 4- 1 |
ACEC
