At the high end of the exposure range, flare in the feather optical system begins to be a problem, resulting in extreme cases in a broad dark sharp edged band considerably wider than the matchline but narrower than the overlap of the projector fields. There are no examples of this in the picture since the region is carefully avoided. These are the major appearance changes in the quality and color of the feather as a function of exposure changes or changes in background.

    Changes in feather quality can occur in maintenance if the lens focus is altered, an imperfect filter is introduced between the film plane and the feather mask, if the feather mask holder is imperfectly seated on its pins, or if the mask falls off its holder and is not recemented properly. None of these effects occur in release prints.

    Color and exposure changes in the matchline occur also with changes in the filter packs. The worst offender was the orange Eastman base. This was avoided by change to a 2/3 nominal thickness of Corning Signal Yellow glass. Avoiding the denser filter values helps by reducing the absorption of energy in any one filter. The use a single glass in the carrier helped to reduce buckling of the filters toward the lamp where they would be heated more, leading to progressively faster deterioration or burning. The almost colorless ultraviolet filter can also be left out inadvertently leading to an orange-yellow shift. Improvement would come from use of all glass (not plastic or gelatin cemented in glass) filters whenever possible, and redesigning the lamphouse to remove the filter packs as far as possible from the lamps in regions where the energy density is low.


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