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Loose pressure plate? (major footage issue - link included)

zachary pape

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Hey guys. Hope everyone is well.

Just had my first roll of 16 processed and scanned since college - super exciting, but the results were very much less so.

The print house suggested it was likely a loose pressure plate. I was curious to the opinions of y'all as well.

Camera is a modded (to ultra-wide) K3.

Thanks a lot



Edited by zachary pape
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8 hours ago, Mark Dunn said:

As your commenter says, shutter timing. The film is moving during exposure. At one point it recovers, so something is loose as well.

Mark is spot on. 100% the shutter is out of sync with the movement. That is what created the image streaking vertically. If it was a pressure plate issue, your footage would be drifting in and out of focus. 


Edited by Gregory Irwin
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Going by the damage to the sprocket holes, my bet is on a short loop. Weak pressure plate springs might allow the film to spring back out of registration with the next incoming claw movement and then a frame may drop leaving the loop short on the outfeed of the gate/pressure plate. 

If you can get hold of some junk film, run that through the camera with the cover off and observe the film movement through the gate/pressure plate. Stop and start the camera a few times. Allow a half-hour rest between at least two of the stop-starts to allow the film to shape-memorise around a sprocket or roller. 

A bend in the film which has become set, may be enough to force the pressure plate away and allow the sprocket holes to move out of registration with the incoming claw. A signature double-clatter after buttoning on some CP16 cameras is caused by shape memory in film which has been resting around rollers for a while, lifting the pressure plate as it passes though.

If this is happening, you should see an initial lift-off then a violent lift-off as the claw strikes the film between the sprocket holes and catches the next sprocket hole as it drags across the lifted film.

Witness marks from the claw between frames suggest the loop had gone short and the claw was punching in, lifting the film/pressure plate, then dragging down the film until it found the sprocket hole and the film/pressure plate sprang back. 

After two slips or maybe more, the downstream loop will have become short and the film will then be pulling through the gate constantly with the claw clattering the film and pressure plate away from the gate. 

The sprocket hole damage is consistent with the upstream face of the claw abrading the edge of the sprocket hole as the film slips back against the gate. 

Another issue may be if the claw crank mechanism is worn. The claw may no longer make full pulldown distance between frames but come up short and punch the film at the beginning of the next pulldown, which may force the film and pressure plate away from the gate. 

The sprocket hole damage is also consistent with the claw punching in against the upper edge of the sprocket hole before engaging with the lower edge and pulling the film down one frame.

The sprocket hole damage also seems to wander sideways which suggests the claw and crank may be end-floating a little. The observed lateral movement would be acceptable as it does not cause the claw to strike the sides of the sprocket holes. However it does suggest there may be some wear. 

Looseness in the claw and crank wearing surfaces, backlash in the gears and the normal nature of the governor in a clockwork drive to hunt for correct speed, combined with dry bearings might be enough to cause the claw to move out of correct registration.

Renewal of lubrication might be enough to put it right but that could be wishful speculation on my part.

Please take heed of more informed commentary from others who may reply.

Edited by Robert Hart
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This is a common issue with K3's, the pressure plate is not strong and neither are the clamps that hold the film onto the single sprocket. It's a cheap design, that can work, but for people who haven't used K3's before, can throw them off. What I do to K3's is remove the loop formers, tweak the clamps and make the spring tension on the pressure plate greater. Those 3 things help the camera perform better. 

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Generally if the shutter timing is out the smearing remains constant. It's rare for shutter timing to shift around, and in a K3 because it's locked by fixed gear meshing the shutter timing is harder to throw out than say a reflex Bolex (where just removing the front will lose the timing).

If the movement of the film during the exposure phase is irregular, like it is here, it's usually because of a loop issue,  loose pressure plate or something like that. The film is being pushed or pulled through the gate when it should be held steady, with the claw sometimes picking up a perf and sometimes missing it. 

K3s are notorious for bad loop formers, loose sprocket guides and weak pressure plates. If someone inexperienced has tried to modify the gate there could be introduced issues as well. 

If the loop formers are still installed, they should be removed. A plunger button retracts them when the lid is closed but often the mechanism doesn't work well and they don't retract enough.

Check that the sprocket guides are locking in and not allowing the sprockets to jump perfs. Check that the pressure plate locks in properly. Run some dummy film through and watch the loop to see if it stays steady (if the loop formers haven't been removed press the plunger down to simulate a closed lid).

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Yes the Krasnogorsk cameras have the shutter and the claw installed together as a "single block" and there should be no reason why anyone would need to detach them from each other during a simple s16/u16 conversion. Nor I see anyone would need to take them apart in this type of camera for any other reason unless wanting to intentionally create a smear effect. 

Intentionally changing the shutter timing would be possible but I don't see why or how anyone would do it accidentally with these cameras because there is no reason for anyone to mess up with the timing of the K3 in servicing by my opinion 

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