Re: Brightness of viewers

[P3D <PTWW@xxxxxxx>]

After his tasty snack on my table of viewer EV values, DrT reported:

> When comparing brightness, the temperature of the source is also a factor.
 
> Experience shows that a bulb that emits "whiter" light appears to the eye 
> brighter than a bulb that emits "warmer" light, even though both register 
> the same EV value.  So, caution when comparing the "white" halogen with
> 60W household or 110 V (in Kodaslide, etc.) bulbs.

This would explain why I was surprised that the reading from the 60w
incandescent bulb was so high.  Subjectively, it seemed about the same
as the T'dRB with frosted halogen bulb.

Flourescent light, on the other hand, seems whiter and brighter than the
halogen lamp's light off the T'dRB reflector.  After mounting a slide on
my $7 18-inch flourescent light fixture (thanks for the idea, Gabriel!),
and checking window placement with my PT'd3D sans diffuser, I put a slide
in the T'dRB...and promptly took the cover off to see if I had the right
bulb installed!  The 15 watt bulb in this light fixture, with thin plastic
diffuser, checks in at EV 15!  Now that's a bright viewer!  Even though
numerically it is only slightly higher than the regular $3 viewer at 0"
from a (used) 30 watt flourescent light, compared to the thin plastic
diffuser of the under-cabinet light fixture, it appears the diffuser of
the $3 viewer is somewhat off-white.

Paul Talbot


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