Pentax 645N occasional winding an empty half frame?

hi,

I recently bought a Pentax 645N, which is my first medium format camera.

It's working well, except it occasionally winds forward approximately half a frame when I meter, which gives me a bit of a a surprise, as well as wasting a frame. E.g. Last roll of 120 came out at 14 shots + 2 unexposed half frames in the mix, not the normal 16.

Some rolls go through no problem.

Does this sound like a fault, or do these sort of cameras like this do things like this? I wondered if maybe the camera decided the roll needed tensioning. Or perhaps I'm not loading the film right?

Any hints would be helpful.

Tom

If the unexposed partial frames are in the middle of the roll, then, no, I'd say it's not normal and may need checking by Pentax (I think they'll still do them). When you start a roll, attach the paper to the empty spool and turn the dial on the side until the arrows on the backing paper line up with the lines on the insert, put it in, turn it on, hit the shutter button - it should whir its way to the 1st frame. When I put in a new roll, I do make sure I don't let it unroll any first. But I've had my 645N for about 15 years (got it when they first came out, I think) and I've never had this happen (knock on wood).

This is not normal behavior for a 645n.

Thank for your decisive comment Jeff.

I haven't seen the fault again since installing fresh batteries and since swapping in a different 120 back, so it's likely one of those two things.