Just so that you're aware, if you stop down to f/11 or smaller, the GA645 is capable of 1/700.
Originally Posted by vlazdir
When I'm seriously unsure about light and other conditions and I want to shoot B&W, I usually opt for either Fuji Neopan 400CN or Ilford XP2. You can expose them at EIs between 100 to 800 on the same roll and still good results. Check out the published specifications for these films; both are C41 process B&W films made by Ilford.
For colour film in similar situations, I usually opt for Kodak Portra 400.