So I accidentally opened up my canon sureshot in dim-ish light. It was a new roll so I had only taken about 3 shots. It’s now showing as S… will it be useless to continue to use the film or can I still take pictures on my camera?
That portion of the film that was still in the canister is fine. Any photos you have already taken are likely affected in some way. I'm not familiar with the Canon Sureshot, but it will certainly require you to advance the film some before you can take more pictures. You can either waste some film and do so from where it is (least risk) or do what one does when switching film types and re-inserting a partially used roll.
If you've never done the partially used roll thing, this could be a good time to learn since you probably have no photos worth saving on that roll.
It's done like this, and this assumes a manual rewind mechanism (don't try it if your camera has an auto rewind):
- Record the number of photos taken.
- Rewind the film until it JUST releases from the take-up reel. Learning how to feel this has happened can be tricky (thus my saying this could be a time to learn).
- Put that roll away and put in the other using standard process.
- When the time comes to re-use the first roll (in your case, the same one), put the film in using the standard process and then take the same number of photos that were on the roll PLUS ONE with the lens cap on (or body cap, if you prefer).
Now, here is the rub, and somebody else will have to answer: How will a commercial lab act if there is a non-standard gap between photos? When I was doing this almost 50 years ago, I was developing my own film, so it didn't matter. You certainly don't want them cutting the negatives in the middle of the photos that are after the gap. That gap is likely going to be just a bit more or less than normal (thus why you take one more shot), at least until you have become an expert in this maneuver. Just starting from where the film is will overcome this potential issue.