Fixing camera slip on Krasnogorsk-3

[Jordan Langmore]

A test roll shot on a Krasnogorsk-3 had the problem pictured in the attached images. The first 10s came out fine but then the frame borders disappeared and the image blurred. I determined that this was likely due to a camera slip, in which the pulldown claw and shutter fall out of sync. I found some information on operating on the gate (http://www.k3camera.com/k3/krasnogorsk-3-front.php), but still haven't gotten info on how to repair this particular problem.

Does anyone have any knowledge on this procedure? Any help would be greatly appreciated!

[Dom Jaeger]

It’s not a timing (shutter out of sync) problem, the film is simply not being registered. You’re losing the frame boundaries, so the film is not stopping, it’s being continuously pulled through the gate.

Have you run some dummy film through to check the loop stays in place? If the loop formers are still there, load the film, then press the plunger down to simulate the lid closing (which opens the loop formers), run the camera and observe the loop. The claw is not properly engaging the perfs, maybe due to a pressure plate problem or the loopformers interfering or an issue with the claw itself.

 

[Frank Wylie]

I have to agree with Dom.  It looks like the film is being pushed through the gate by means of the loop formers, rather than being advanced by the take-down claw. 

The Krasnogorsk has a terrible auto loading feature and the loop formers tend to be more of a drawback than a help.

We had two at Ohio State University and I wound up removing the loop formers entirely and having the students manually thread the cameras.  This helped somewhat, but the gate and take down claw are not well made and it could still lose the loop when the pressure plate spring became fatigued.

If nothing else, find a way to fix the loop formers at maximum distance from the gate and manually thread the camera with a dummy roll to see if this solves the problem.

It also helps to NOT let the camera spring tension totally run out during a take, as the film can slip in the gate while winding the camera and cause the film to lose a frame when the spring re-tensions and the claw cycles partially until the trigger stop engages.  This small bit of movement, against an area of the film that has no perforation, will cause the loops to become uneven.

Eventually, with enough takes, you will lose the upper loop due to this frame skipping and the problem will manifest itself.

Edited February 26, 2022 by Frank Wylie