Ghosts in the machine?

Austerby

Austerby

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A strange pattern has started to emerge: my 1936 IIIa has developed a peculiar habit over the last three or four films of inserting about a half-frame jump roughly around exposures 23 and 24 on a 36exp roll. Every other frame gap is as neat and regular as one could wish for, but then a larger gap appears, then does not further occur. I don't think the camera is in need of a service as it is working perfectly as regards shutter speeds, fast and slow.

When it first occured I thought, well, it is seventy one you know. I can't recall noticing it on earlier films, but all of the past few have been the same - noticeably always around the early twenties. (They've all been HP5+ if that helps.) I haven't noticed any longer winding times during usage but then I suppose it wouldn't have a particularly strong effect, topside.

If you would like me to, I can scan one to show you (I have just processed the latest example and it is currently drying in the bathroom) though my description is accurate.

Have any other forum members comparable experiences or plausible explanations? A perplexed Austerby anxiously awaits your learned thoughts....
 
Austerby, are the sprocket holes at the edge of the films okay, nothing wrong with them? When you load your film do you take up the slack by turning the rewind knob until the film is snug?

Regards,
Tom
 
The film loads properly; the edges and all other separators are millimetre-consistent. Attached shows what is happening.

BTW I'm not especially worried about this as it doesn't seem to have any unwelcome side effects, but I am curious as to why it has re-occured.
 

Attachments

I have a IIF that would break a 36 exposure roll of film after just about the same number of exposures as the film was advanced.

The camera had just come back from having the shutter curtains replaced (Essex) and was under warranty. I returned it to the shop and they corrected the problem.

I have no idea how the problem was corrected so I don't rule out excorcism.
 
It is kind of perplexing since the film advance is being taken care of by sprocket teeth and it only happens at one spot in the film roll. That spot is 20 some frames into the 36 frame roll. Hmmm! Doesn't make a lot of sense why just that one spot 2/3 of the way through! Did you notice anything peculiar about the feel of the advance at that point? You might have to waiste a roll of film by loading it and leaving the bottom off and watch as you advance and fire the shutter time and again until the roll is used up. You can rewind the film and do it again if necessary to watch it again and again. You might also do this with the lens removed so you can watch the curtains as well.

Regards,
Tom
 
So the film is slipping about 2/3 of a frame. That can only happen if the film is lifted off of the sprocket wheel teeth. That can only happen if film tension on the take-up spool slacks enough to lift the film. Strange indeed.
The sprocket wheel itself isn't slipping, because then you would have a double exposure instead of a large frame spacing.

Exorcism!
 
The "slip" between the take-up spool and the wind shaft might be too much. That could let some slack develop. Or it could be sticky, and let go all at once, again forming a short film loop not engaging the sprocket wheel.

Or maybe there's something wrong with the mechanism that opens the gear train when you swing the lever to Rewind. The sprocket wheel is loose when the rewind lever is on R, and you can wind endlessly.

This might get tickled by some other problem with the slip clutch in the take-up area.
 
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