Shot on my Pentax 645N. Never seen this before but I could have been using a different back to my usual one (I can't remember if I changed them over or not) and the seals look to be missing compared to my other back. On the other hand, it only seems that the light has been leaking in from the left hand side. I'm not sure what a fat roll looks like but, if it were a fat roll, I would not have thought every frame would be affected on the roll and also completely across the frame from top to bottom .
I suppose the other possibility is a mistake at the lab.
I have seen something similar even not as severe when using one of the 6x6 backs for my Hasselblad 500 C/M. IMO definitely a light leak - in my case it was caused by missing baffles/seals which a former owner (I bought this film cartridge used) had removed most likely to put them into another back. I ordered the missing parts and replaced them myself. Works fine since!
Fat rolls are super easy to spot. The roll will not appear to be wound tight and if you squeeze it you will be able to compress it. With a properly tightly wound roll you would not be able to squeeze it.
However, fat rolls would show light leaks on both sides, and only on the last few frames.
Yeah, I think it must be a light leak. I think it is the only way one could have the whole length of the film fried in this way. That's what you get for buying a mint minus insert from ebay. I'll revert to my old insert and replace the seals on this one.
Expensive mistake having toasted a roll of portra and ektachrome.
