In article <4b6err$h9l@halinalle.cs.hut.fi>, ilu@niksula.hut.fi says...
>I'm not sure if the response of the _meter_ varies
>significantly with wavelength.

Hmmm... If you want to see color response error clearly, photograph
flowers close up! The saturated reds will have you moving ASA 40 film
down towards 25 ASA (and even lower) in a hurry to avoid dark slides.
Also, try metering off a grey card without, then with red, orange,
dark yellow, green and blue filters with known filter factors - you
will notice considerable error between the meter readings and the
(filter factor) predicted readings, unless your meter is color
corrected. BTW, the old selenium cell meters (yuh, those antiques)
have less color error than most modern meters. But, as I said before,
unless the colors being metered are fairly saturated, you may not
notice the errors.
Hope this helps.