|
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.
|
