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Assuming Camera #1 for example that
the calibration is correct to plus or minus 1/16 stop and that settings are
made always in one direction to minimize backlash effects (and this is made in
the direction from which the lens was calibrated), the weight of the protruding
lever can still cause a drift due to the effects of gravity when the camera is
jostled or vibrated severely in the absence of a friction or locking
arrangement. Even without this problem the operator would still have
difficulty reading the scale this close.
The deficiencies of the Camera #1 diaphragm control have
been long recognized and has led to the incorporation of the type used in
Camera #2. Here several deficiencies are noted. First, the mechanism easily
becomes bound up, imposing disproportionately high forces on thin diameter
connecting shafts which twist, tiny collet type clamps which slip, and tiny
gears and universal joints which can have too much backlash, all of which lead
to incorrect settings of the diaphragm. In addition there is the possibility of
coupling the magnetic disconnect joints a full turn or more out of position,
instances of which can be inferred.
Even if the mechanism were perfect, there remains the
initial setting problem and the presumption that the diaphragms track exactly
within 1/16 stop. There is still needed reliable equipment or technique for
calibration. The one presently employed have certainly helped but are
inadequate.
The printer, too, can contribute to panel errors. When too
short a timing pulse is given to the light change unit, errors as great as two
printer steps have been noted, a type of error which was corrected by
lengthening the notch or could be corrected by a "slug" or time delay relay.
Burning the lamp at too high a voltage can cause appreciable fading of the lamp
– or more important in our particular case – burning, fading, or crinkling of
the filters during the interval required for printing separate panels.
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