Quote Originally Posted by Jim Noel View Post
"And B & W film tends to be slower with tungsten sources."

Boy is that an outdated fact. The difference today is so minimal as to be a non-factor.
There is about one stop difference according to my sensitometry tests. Acros is the worst of the modern films but those with extended red (SFX200, 2405) show no difference.

It depends of course on your meter. If your light meter is lacking in red sensitivity then you won't observe the effect and the extended-red films will look faster!