I've found the easiest way to grab frames from film is to put the print
through a PhotoCD machine and scan the frames. PhotoCD creates five
scans at different degrees of resolution, of which the second-best will be
most appropriate for print reproduction.
Where do you get access to a PhotoCD machine? Find an independent lab who
will do this for you on a fee-per-hour (rather than a fee-per-image)
basis. Needless to say, you have to do this at an independent facility
located in your community. Expect to pay about $2 per shot.
There are two other alternatives:
1. Buy a Duplicon from Century Precision Optics in Burbank, Calif. They
are expensive. It's a lens adapter (like a slide copying attachment) that
copies 16mm to 35mm.
2. Transfer film to tape digitally and make frame grabs from the digital
videotape. Again, this is very expensive.