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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: net.analog
Subject: Re: Re: does the eye see light linearly?
Message-ID: <525@kitty.UUCP>
Date: Fri, 25-Oct-85 23:18:13 EST
Article-I.D.: kitty.525
Posted: Fri Oct 25 23:18:13 1985
Date-Received: Thu, 31-Oct-85 21:27:19 EST
References: <142@drutx.UUCP> <20100001@inmet.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 25

> This is sketchy info at best, but it may point you in the right direction.
> I had a job once in a place that made stage lighting controllers.  The
> dimmers followed a decidedly non-linear curve which was some sort of standard
> for theatre lighting. I can't remember the name of the standards organization
> nor can I remeber if the curve followed human perception of "brightness" or
> just offerred lighting directors more control in the low end.  Sorry to be so
> vague, but it was a long time ago.

	That's because lamp input voltage versus output lumens is a distinctly
non-linear function.  A linear scale autotransformer or thyristor dimmer control
would not be useful due to lack of resolution at the high end of the scale and
too much deadband at the low end of the scale.  I don't believe there is a
standard for stage lighting control curves; this was pretty much an arbitrary
decision on the part of stage lighting manufacturers.  The large variety of
lamps used in stage lighting applications (from PAR-38 to bipin to quartz
halogen, etc) have such different curves of voltage versus lumens, that a
meaningful standard would be impossible to set.

===  Larry Lippman @ Recognition Research Corp., Clarence, New York        ===
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