Dear Dr. G.
        I want to thank you for all your wealth of technical information on this and a host of issues.  Light is one of the subjects for which I have some background and interest.  I graduated from Rochester Institute of Technology in Photography 30 years ago and acted as a professional since that time.

Could it not be possible to simplify the analysis of all different types of lamps by configuring different, and comparably rated "white light" bulb/lens configurations and then simply measuring their output on a target of white with an incident light meter.  Additionally a spectrum analysis could be done to tell us the color temperature of the various "white light" fixtures.

I am most interested in whether a light will be bright enough, controllable enough, soft enough, financially feasible, easy to install and render a "faithful" view of the subject without distorting big chunks of the spectrum.

Your the man!
Bob

Once we knew how much output of usable light are available from each type fixture (fluro
incandescent and LED) we would be able to test (by use) the cost/life of each fixture.  Perhaps someone has done such simple testing but I haven't seen it.
At 07:52 PM 4/21/01 -0500, you wrote:
Between the CRC Handbook of Physics and Chemistry and the Illumination
Engineering Society Handbook, I should be able to come up with a set of
factors for comparing lumens, candela, and mean spherical candle power.
I know small lamps, such as automotive lamps (might find some help in an
SAE handbook also), are rated in mean spherical candle power. Lamps that
are more focused, I'll need to study on. I did find the light meter that
is calibrated in footcandles. Right at the moment, laziness has
overtaken me and I doubt I'll accomplish more than finding the IES
handbook this evening. Because I don't have electronic equipment in my
dark room, I can only experiment after dark.

The 1141 lamp specified for the ceiling fixtures in my Caravel are rated
at 21 MSC each to give a starting point.

Part of the tower of babble is that some of these units are metric, some
are US, and some are SI metric.

There is a table in the manual for this light meter that correlates its
readings in incident foot candles to EV and exposure. There is also a
formula for that.

Mean Spherical Candle power is measured with a white sphere (coated with
magnesium oxide, the whitest of white) with the lamp under test at the
center and a light meter at a hole in the sphere.

Gerald J.



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