Quote Originally Posted by TheFlyingCamera View Post
Roger- the reason not to use a 400 film, especially with smaller formats, in the studio is that you lose the ability to choose the aperture you want to use for depth-of-field control. The same is true for field use, sometimes to a greater degree than in the studio. If I have 400 speed film loaded, there's a good chance if I'm using strobes in the studio that I can't dial the power down enough to use f5.6 (for example) and keep the lighting quality that I want. When dealing with 35mm, it's even more likely to be a problem if the aperture you want to use is say f2.8 for depth-of-field purposes. Yes, there are ways to compensate by adjusting focus to have the main subject at the very rear edge of the depth-of-field, but that too has its own issues.
That makes sense in the studio. It rarely makes sense for me in the field which just doesn't seem to be that bright. Shooting in bright sun is rare - overhead lighting is not usually good anyway, when the sun is high. And there are always ND filters. Considering the difference in speed is, as folks pointed out, 1-1/3 stops that's just not a huge difference. It's not like Portra 400 versus the old Ektar 25, say.