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Luminance fluctuations



Hello all,

Yesterday I transferred 4000ft of 16mm ('79 - recent stock and recently
exposed) shot at 24fps.  It was shot inside an apartment with available
incandescent lighting, but next to a window with cooler exterior light.
This was an interview conducted from mid-afternoon throughout the
evening, so the exterior light became less and less of a factor.  I
don't know what equipment was used, and I don't believe there was any
other lighting than that which was in the apartment.

OK . . . here's the question.  Throughout the shoot there were subtle,
uniform, luminance dips of approximately 1 - 2 IRE (this message has
been cross-posted on the TIG, so, for the non-video techs, that's on a
scale of 100) over 1 - 2 film frames and then recovery back to original
lighting/exposure? within 2 seconds (the recovery was practically
unnoticeable.)  These dips occurred usually every 20 to 40 seconds
(sometimes longer, sometimes shorter), but other than that we were
unable to discern any pattern.

We also put the film on another telecine, in another room, to rule out
that factor and observed the same problem in the same locations as they
were observed in the first suite.

No extra lighting, no pattern, etc. . . . any hypotheses?

Best regards,
Tim Bond
DuArt Film & Video



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