Digital BW, The Print

if the subject is fully 
> sunlit and the light is coming from behind me; I get the expected 
> reading of F/8 @ 1/500 of a second. 

Actually, in full sun, ISO 100 would yield a correct exposure of
ƒ8 @ 1/400 or ƒ5.6-2/3 @ 1/500. Your are already 1/3 stop
off. 

Another wierd thing about digital cameras- camera processing software
does have an impact of how the image looks. I have an associate at an
in-house studio and he was 
photographing sinks on a grey laminate surface for a catalog. He was
using a Nikon D1x with a manually set exposure of ƒ8 @ 1sec under
studio lighting. A grey stainless sink 
looked perfect on the monitor and densitometer readings read ok. He
swapped out to a white sink, (a common technique when doing high
volume catalog work)did not change 
lights or exposures and the resulting photo of the white sink was
darker. The grey backgrounds did not match. It appears that chips may
be influenced in part by the subject 
matter, and the camera processing software seems to want to take hold
of the image and fiddle with it even when exposing manually.

John Luke