As a rule of thumb, I rate my colour neg films a stop higher than their box speed, e.g. ISO 100 film shot at EI50 as I read some time ago that it allows for better shadow details without blowing out highlights.
Howevever, I shot a role of the newer Fuji Velvia 100 the other day at EI50. The pictures I got back from the lab do look great, but they are much brighter than I expected them to be.
Should Velvia always be shot at it's box speed and is it less accepting of this technique (I read Velvia is particular about exposure) or are these brightness aspects more likely to be due to my exposure in camera rather than the EI50 setting?
I can't paste the link, but if you're interested in looking, it's www.tedsmithphotography.com, click 'Portfolio' --> 'Landscapes' and then scroll to the bottom. They're the one's labelled 'Combe Martin Bay'.