It can be helpful to put the negative inside the camera as it would have been when shot. And pay attention to areas of film before and after the actual image area as it comes out of the cassette and goes around the take-up spool. For example, the fogged area below the Christ figure appears to have a hard edge on one end and a fuzzy edge on the other. I forget the size of the Canon 7 and film path, but I wonder if this section of film was exposed between the film cassette (fuzzy end) and image gate (hard end). Meaning the leak is in the cassette chamber. Well, just spitting in the wind here but you get the idea. Sometimes the film tells you exactly what happened. Sometimes! Light leaks can be very difficult. Good luck!