[VAC] Re: LED light bulbs-prices

[Dr. Gerald N. Johnson, electrical engineer]

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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