I've been thinking about getting into film photography for a while, so recently I grabbed the old Olympus OM-1 from work when they were cleaning out the media cupboard, I'm only mentioned in this so you can understand my experience level with film is minimal. I've shot a few rolls of film for testing and in a couple of them have seen some strange light artifacts, but only in a few of the shots. Rather than try and explain them, I'll show some examples (scanned 6x4's on flatbed scanner, so please excuse the quality):
I also have an example of the orange triangular artifact above on another shot that is much stronger and on a dark landscape shot, but thought it would be useful to show 2 shots that I know were taken close in time.
The lighter bar down the left hand side of the above shot appears in a few other shots as well, although with much stronger effect. I've also seen a bar down the side of other shots, but orange in colour rather than white.
These artifacts aren't occuring on every shot, I have shot 3 rolls of film and have found these artifacts on 6/24 or so per film.
My suspicion is that there is a light leak, or multiple light leaks. I've changed the seals on the back door already, but the question I am not sure about it ... is there any other way for light leaks to occur in a film camera that I can investigate? Am I on the right path or is this likely something else ... or a combination of things?
Are the images with the orange artifacts usually the first shots taken after the camera has been unused for a while (hours, days,etc.)? In other words, the frame in question sat directly behind the shutter for longer than just the time between frames in the same session?
I just had a look at the shots in order, and yes, it would seem that the shots with the orange marks would have been the first shots for some time (probably at least a day in all cases).
All the the film shot thus far has been processed by a local professional camera store, so I don't suspect processing at this stage.
update: I've shot another roll through the camera. The good news is this time I had no artifacts appear, however I am conscious of the fact that this film was shot in a matter of hours, rather over multiple days that the films that I had issues with. Now that I have some time I'll try out the light inside the camera idea that Alan Marcus suggested, an LED with a small battery should do the trick. Note I haven't tried this yet, but something like an LED Throwie should do the trick, just don't attach the magnet!. Here are some instructions for anyone not electronics inclined, they are pretty simple to set up