Strange viewfinder issue with K3

Patrick Cooper · July 30, 2022

I have a Krasnogorsk 3 which stopped working a long time ago. I can't wind it up anymore. Today, I pulled out the camera and had a look through the viewfinder with the original stock lens attached. Everything looked normal. I then mounted a Takumar 200mm f3.5 lens and looked again through the viewfinder and I could see a dark patch obscuring the right side of the screen. About a quarter of the viewfinder is dark (on the right hand side.) I also don't recall seeing this obscurity the last time I took out the camera over a year ago. I mounted the stock lens again and the far right of the viewfinder is still dark. I also noticed if I tilt the camera up while viewing a florescent light on the ceiling, the light becomes distorted at the top of the dark patch. Would anyone have any idea on what this is?

Aapo Lettinen · July 30, 2022

is the mirror shutter correctly aligned?

Krasnogorsk cameras are relatively easy to open and service by yourself so if the camera is not working at the moment I suggest you trying to repair it, it is fully possible you get it working again. Of course if the spring itself is broken then it would not work (though could be still used for shooting hand cranked shots if you keep the trigger depressed or remove the trigger mechanism so that it can turn freely)

Patrick Cooper · July 30, 2022

I thought the issue could possibly be related to the mirror shutter but I'm not sure how to adjust it. I don't suppose it can be pushed out of the way by hand?

And that winding key is all loose. There is no resistance. One day, years ago, it stopped working out of the blue.

Edited July 30, 2022 by Patrick Cooper

Simon Wyss · July 30, 2022

The spring is prone to jump off its arbor. USSR didn’t care for a hook proper. Repair job

Dom Jaeger · July 31, 2022

For positioning the viewfinder image the mirror shutter doesn’t get adjusted, the prism to the viewfinder does. There are multiple adjustment screws visible when you remove the front. On a K3 the ground glass is fixed.

On any mirror/shutter reflex camera the spinning mirror needs to run flat and true. You normally can’t change the shaft angle, and any change of the mirror angle relative to the shaft would cause the image to wobble and vibrate. The only possible adjustment that doesn’t destroy the image is mirror height, which changes the ground glass focus. All theoretical in a K3, where most settings are pinned, except the viewfinder prism.

Aapo Lettinen · July 31, 2022

I meant that it sounds like that the mirror shutter has just stopped halfway through the frame and thus it is only partially reflecting the image to the groundglass. The krasnogorsk shutter is pretty impossible to get to wrong alignment without using lots of time and effort and I don't see how the groundglass or prisms could suddenly go out of alignment in storage if the camera is not dropped or otherwise mishandled. But if the spring is not wound then the shutter can be in any position for not having the spring tension to rotate it to the viewing stop position. One can probably rotate it by hand if necessary, the mirror gets fingerprints but the shutter is made out of aluminium and you can't accidentally destroy the shutter by just touching it unlike on most other cameras. The gear mechanisms of the camera have some low durability gears though so if the mechanism is just plain freezed up then it is necessary to open it to first diagnose the problem.

The shutter is stopped to viewing position if there is any tension in the spring so that it is not completely run out after the take... just like in most other spring cameras as there is a hard stop in the trigger mechanism which always stops the shutter to the same position if there just is some spring tension capable of moving the mechanism at all. If the spring system does not work then the mirror can be in any position and your current situation sounds just like that. Why the spring motor does not work is another issue but seriously, these cameras are easy to take apart and it is much easier to open it to see what the real problem is than to try to speculate on a forum ?

Dom Jaeger · July 31, 2022

51 minutes ago, aapo lettinen said:

I meant that it sounds like that the mirror shutter has just stopped halfway through the frame and thus it is only partially reflecting the image to the groundglass. ?

Ah right, yes very possible. Easily tested by turning the mirror by hand, as you suggest.

52 minutes ago, aapo lettinen said:

Why the spring motor does not work is another issue but seriously, these cameras are easy to take apart and it is much easier to open it to see what the real problem is than to try to speculate on a forum ?

Very true!