>Date: Mon, 30 Oct 2000 18:39:47 -0800 (PST)
>From: Acer V <siddim01@xxxxxxxxxxxxxxx>
>Subject: [OM] [ot-ish] florescent lights "blanking" at 1/60sec
>
>i did a few rolls of indoor office building shots (clinic) this weekend,
>and looking over the shots, it seems that some of the overhead recessed
>lighting fixtures seem only "half" on, that is on side lit, one side
>dark. in shot shots, the whole fixture is dark. could it be that the
>shutter was open during the "off" cycle of the 60Hz lamps?
yup. Flouescent lights flicker at 120hz. If you set your computer moniter to
60hz in a room lit by flourescents, it will drive you crazy. This isn't a
problem with incandescents, since they "burn" and diminish in output only a
very little amount during zero crossing. Flourescents operate on a different
principle, which is ionization of a gas. This turns off immediataly and
completely at zero crossing. You have to use a slow shutter speed of less
than 1/60th to avoid problems. This is also true of photographing TV
screens, etc.
Be seeing you.
Dirk Wright
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