Here are the ISO/ASA (No one really uses ASA anymore, but my old Pentax still has ASA on it) assigned numbers for film speeds, enjoy.
- Slow Film (ISO 25-100): Ideal for photos in bright light. They are very fine in texture, be aware, without flash, in dim light, you may get camera shake without a tripod.
- Medium Speed Film (ISO 200-400): Your all-purpose films. You will get quality like slow film, but it is much better suitable for low light photos, like dawn or dusk. After about ISO 400, most compact cameras won't read the film.
- Fast Film (ISO 800-3200): Exclusively used for low-light photography where flash can't be used as well as for high-speed action shots. Fast film will give a very grainy photo however, but that's because of the chemicals in the film that allow it to be used in dim-light so well.
Sources
Hedgecoe, John. John Hedgecoe's Photography Basics. Sterling Publishing Co. New York. 1993