Because you say that the mark is a fine, straight line, I think it almost has to be from some mechanical cause, like grit in the film path somewhere within the camera, or a nick on the pressure plate: something like that. Static marks show up as "stars" or "lighting bolts" in an irregular pattern, not the straight line you mention. Alan's question about whether it appears in the leader portion of the film is a good one. Another thing that comes to mind is how you are handling and loading the film into the tank. Some tanks come with various gadgets to help get the film seated into the tank grooves. There is a possibility of some kind of sharp edge there too. Possibly chemical contamination, though I dont think that would make as sharp a mark as you describe. Get out your strongest loupe and examine camera and processing equipment as carefully as you can. Use your fingertips to see if you can find any hint of a rough spot anywhere.(posted 9127 days ago)Oh, one other thing -- is this mark only one one type of film that you bought at one time, or does it show up on all your films, regardless of type, and when purchased? If only on one type of film, indicates possible manufacturing fault. If on all of them, most likely your equipment. Good Luck