When I do shoot portra 400 I normally shoot it at 250, as that's where it looks best to me. But If I'm in a situation were I have to get the picture I will shoot portra 400 up to 3200. I know I'm going to be loosing detail, colors and adding grain, but getting the picture is better then no picture at all. And I have done this on paying jobs where it was dark and flashes where not allowed.