Another harmful effect in the blend lines is flicker. This may be due to runout on the feather sprocket. Runout of the full fitting teeth should be held to about .0001" full indicator reading. This shows up if present as a flicker frequency of a little over 2 per second and is very regular. It may not always show up because the effect for adjacent panels may be more or less out of phase. Flicker may also occur of more or less random frequency, particularly on starting, due to uneven rate of rotation of the feather sprocket, varying the exposure time. It may be checked by introducing about an 0.60 ND filter in the feather pack and plotting density of the track on a densitometer at each perforation. This effect may be caused by too light a holdback tension on the positive feed roll, by eccentricity of any or all idlers to the feed sprocket of the printer, sprocket eccentricity or wear, gear and pulley eccentricity or wear, belt wear or fluctuation of motor speed. If a density check of the track does not show error, the cause is likely to be found in projector weave, which is just as critical and must be held to the same tolerance as the feather sprocket.

    An unusual effect is the occurrence of fixed dark areas of the feather corresponding to the sprocket holes, giving a somewhat beaded effect in the matchline. This is due to reflections from the feather-sprocket teeth during the feather exposure. This is easily checked since the feather strip should stop just at or within a few thousandths of the perforation edge. A special adjustable mark has been added to Printer #1 to correct for this effect, and it will also be necessary in Printer #2. No instance of this effect is found in release prints although an effect which can be confused with it does occur where there is edge fog in the negative. The distinguishing feature is that the edge fog phenomenon is most likely to be colored, usually orange or orange-yellow.


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