220 headaches

I spent way too much time trying to calculate film
length per turn as the film builds up on the spool and
the diameter increases. I kept coming up with length
per turn, but turns per length eluded me. You want a
constant length.

I finally put a developed roll of 220 in with leader
paper and empirically measured number of turns. I had
some inconsistency. The only mathematical solution I
found that was heading in the same direction as me,
was to note that the diameter of the spool increases
by a consistent percentage with each wrap of the
film...this is still entrenched in length per turn and
not turn per length, but I just counted how many turns
to get to the first frame and how long to the next
then multiplied the incremental turns/frame by the
percentage of diamter increase because it was directly
proportional.

This still didn't agree with what I measured. Part may
have been not knowing that for examply 6x9 is really
typically 5.6 x 8.2.

Anyway I made a chart to luggage tag on to the Moskva.
I'll find it and scan it. It is a bit overly
conservative and it's hard to accurately count
fractions of a turn much smaller than 1/8, but it's a
start.

I'll be back with just a picture, since I already did
the 1000 words part.

Murray

                
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Received on Fri Aug 5 22:55:22 2005