Posted by nobody special on 01/11/41 11:50

If this was old, old footage from the early 80's , the 70's or 60's, it
was an artifact of the plumbicon and saticon and orthocon pickup tubes
of those old cameras to go black where the video was too hot. You can
see this a little bit in the Beatles on Ed Sullivan and things like
that. Very distinctive period look, and hard to emulate today... some
guys keep old cameras from that era to rent out for directors who need
that period look. Unfortunately, when the levels were that hot, the
tubes usually also "burned', that is, got permanent discolored streaks
on the images that lingered long after the light source had moved off.
just as if your eye looked at a welding spark without protection too
long. often, after a big concert in those days, the tubes had to be
replaced at high cost after one performance. Sometimes you could
massage them back by pointing the lens at a full-screen white card long
enough to average-out the burn, but while this sometimes "erased" minor
tube burns, it shortened the overall life of the tube and it's
sharpness.

I know of no modern camera that has this artifact; the most common
artitfact of CCD digital chip cameras in bright lights like that is a
vertical streak. The new foveon-type CMOS chips have a different
reaction.

If the cameras you saw were hooked into a switcher, the operator
*could* have set a luma key to black or any color, but it would have
had to be adjusted to only a narrow, very bright part of the signal to
only be seen in the bulb areas of the hot lights and in no other
high-white part of the picture.

Sorry i can't be more help than that.

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