converse is true of the larger diameter rollers: they exert less strain on the
film but occupy more space in a processing machine.
Some processors have
rollers of different sizes and it is important for a technician to know these
sizes and their locations. This will frequently make it easier to pinpoint the
cause of a mechanical processing defect. For example, if an abrasion appears
approximately every three inches on a roll of film, the cause could be a small
(one-inch diameter) roller. If, on the other hand, the defect is found every
nine inches, the smaller rollers could be eliminated as the cause and the
larger (three-inch diameter) rollers would be inspected.
2.
Machine Threading Systems.
a. Leader Type. Most processing machines are pre-threaded with a leader
which may be thick or thin acetate, mylar, or in some instances, clear film,
thereby rethreading the machine for the next processing run.
b. The threading pattern used most often with wide film (over 70mm wide)
is the "over-under system." Normally when this pattern is used, the emulsion
side of the film touches only the bottom rollers which are always wet with the
processing solutions (figure 1-2).
However, one processor now being used is
operated with the film emulsion down which means the emulsion side touches the
top rollers and the base side touches the bottom rollers.
Figure 1-2.
Over-under threading
4
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