Slight fogging on 120 film after removal from Yashicamat 124G

Cleaned the inner face of the taking lens on my 124G over the weekend and ran a roll of HP5+ through it as a test. The wet negs look nice and sharp so I'm happy with the cleaning job.

Upon closer inspection there is intermittent mild fogging which is quite sharply delineated from about frame 7 onwards. The fogging is almost rectangular shaped and extends about 4mm into the frame from the rebate edge of the film. The fogging is not continuous across all frames from 7 onwards.

I noticed that the wind on became a bit hesitant around frame 10 but I was able to exposed all 12 shots. When I removed the film it didn't feel to be properly tight on the takeup spool. I tightened the backing paper as best I could before licking and sticking and putting the film in a black plastic bag I keep for this purpose.

I am certain this light strike occurred after the film was removed from the camera and I'm curious as to why the film didn't roll tightly onto the takeup spool. Once the first two or three frames have been shot the film and backing paper should be fairly well self-centred from the supply spool through the film gate and onto the takeup spool. This should allow the film to sit 'flat' and square on the takeup spool. It's almost as if the backing paper was binding between the flanges on the takeup spool allowing slack to creep in.

The previous film I shot in this camera was TMX 100 and this film would have supplied the takeup spool for the roll of HP5+ that I just shot. Is there a possibility that there are minor variations in the width of backing paper between manufacturers which in this case may have caused the film to bind and not roll tightly onto the takeup spool.

I'll hunt around tomorrow for my digital calipers and measure the width between flanges and then the width of the backing papers I have on hand. If there do appear to be differences I guess I shall have to make sure that I use the widest takeup spool I have for all films.

I look forward to your comments and observations.

Have you seen this thread?
(there was a url link here which no longer exists)

Once the backing paper is set into the takeup spool it does not shift. If the paper was misaligned it will be crimped on one side. The takeup spools will be within .001 inch in the inside width. If the film is winding loose then increase the tension on the supply side spring(s) of the camera.

Look at the silver film rollers. Are they level? Are the frames of the shots square to the film, or slightly canted? If one of the rollers is not level it will cause the film to wind at an angle and bind.

When you start the film, put light pressure on the film roll as you wind forward to the start mark, using a finger or two. This will keep the film taut as you wind, even though it will move up a bit and relax as you go to close the back. I am basing this partly on my experience of loose winding on a Fuji GS690, which leads to just what you describe. I can't remember having this happen with a TLR.