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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