In article <01bbe926$18e85910$448c389d@a-dougsc>, a-dougsc@microsoft.com says...
>James Grove wrote in article
>...
>> Can someone tell me how to use a grey card, thanks.

>Grey cards reflect a percentage (18%?) of the light that falls upon them.
>This approximates the reflection of most caucasion skin. In a pinch you can
>always get a reading from the palm of your hand.

Umm, I don't think that this is true - average Caucasian skin is about one
stop lighter than 18% (middle) grey, which looks relatively somewhat dark
(as will the slides taken following the advice above ;-). You can use the
card pointed back toward the camera, in the same light as the subject,
to read incident light, or you can use a hand (with the appropriate compensation [one stop overexposure, for Caucasian skin tone]). BTW,
grass meters about one stop darker than middle grey and can also be
used for substitute readings, as can snow, which can be placed about
1 2/3 stop away from medium grey (open up 1 2/3 stop from the snow
reading taken with the meter pointed in the general direction of
the photo to be taken).
Hope This Helps