Hi Steve, don't forget that if you are stuck in a situation of film speed at ISO 100 but need to increase that because of the lighting situation, you can safely do what is known as 'push' the rating by upto 2 stops. Which means you override the camera setting of the ISO rating (from 100 to 400 for example). You can then continue to use the fim at that ISO rating safely. However you must remember to tell the developing lab that this roll of film has been 'pushed' and preferably put a sticky label on the roll indicating the new ISO ratings so it can be developed and processed at the new rate. The draw back of this is often a higher grain of film which will be noticable in your final image. But, as indicated earlier this can compliment an image, depending on what the subject is. But, it has to be better than no image at all. I hope this helps.
Regards....Phil

__________________
Regards....Phil

If it moves shoot it. If it doesn't move, still shoot it.