[visionlist] Scotopic (il)luminance measurement

[Gislin Dagnelie]

I am looking for suggestions regarding measurement of scotopic
(il)luminance in 
the absence of a scotopic spectral sensitivity filter, photomultiplier
tubes, and 
similar tools.  

The condition I am trying to measure is a room illuminated by
incandescent light 
with a rheostat turned down to its lowest level.  In other words, the
spectral 
characteristic of the illuminant is in the long wavelength range, in
fact peaking well 
outside the visible wavelengths.

Simply attenuating an incandescent bulb with ND filters until you reach
an 
(il)luminance level matching that of the room light and then measuring
the 
unattenuated (il)luminance, even with a meter equipped with a scotopic
spectral 
sentivity filter, is not going to do it because the color temperature
of the light 
source would still be very different,

Thanks for any suggestions you may have.  Please send them to me
privately, 
and I will post a summary on the list later.

Gislin Dagnelie
Lions Vision Center
Johns Hopkins University