On Wed, 25 Dec 2002 12:43:38 -0500, Alan Browne wrote:

>Light metering is not an easy thing to test. If you have a 100W red
>light and a 100W blue light, do not expect them to meter the same. And
>this is not due to the meter, but to the actual output of the lamps with
>different pigement filters on them. Same thing for reflected light.
>
>Films are the worse culprit (by far) in terms of spectral response.
>
>I have found two references stating that light meters are "corrected" or
>need to be corrected for color. But I can't find what the range
>(intensity) is accross the visible spectrum. If you can find those,
>I'll happilly reverse my opinion.

At least for the colors of B&W filters, like dark yellow
(FF2 = 1 stop), orange (FF4 = 2 stops), and red (FF8 = 3
stops), you can easily find the meter color errors
compared with flat for these colors by comparing the
meter readings of a grey subject without and with the
filters in front of the meter, keeping all else the same...
Applying the corrections with the film of interest shooting
the grey subject with and without the filters (and doing the
same without the corrections) and comparing the "grey"
densities on the film or contact print will indicate whether
or not the corrections were needed. For my gear and films,
I found the meter in error (underexposure) by about 1/2 the
FF for each of the colors above compared with the grey
no-filter exposure...