candleflame luminance below 20 kcd/m2

[Jan Hollan <jhollan@amper....muni.cz>]

Dear Paul,

thank you once more for the daylight/moonlight formulas. I've implemented
them into my overview of days and nights in Brno, as available on
   http://amper.ped.muni.cz/weather/

Searching for zodiac light luminance in your radfaq, I've noticed an error
at the end of part 10. Namely, the luminance of a candleflame cannot be
much over 10 000 cd/m2 : the whole flame has some 1 cd, and its
cross-section is just somewhat below 1 cm2.

To see what the real values are, I've made some images of such a flame.
The results are at
   http://amper.ped.muni.cz/light/luminance/candle/

It appeared, that my candle had just 16 knit in the brightest part of its
flame. So, 2e4 cd/m2 is a safe upper value for such a flame. Can hardly be
more than that.

sincerely,
 jenik

PS.

 Some one or two years ago, Barry Clark explained me why Englishmen don't
use ``nit'' as a name for a unit. It has namely another meaning in a
popular language... People using nits (as astronomers speaking about night
environment) might be called nitpickers, to stress they need not be taken
seriously. So I'm further using nits in Czech, where they sound neutral.
But avoid them in English now. Of course it's boresome, when I need to use
a luminance unit twice in each row of a text...