Exposure Window Light Leak on my Sputnik

When I use my Holga, I do not get any light leaks from the exposure window even though it is always 'open'. However, in my Sputnik camera, I get a frame ruining diagonal leak (see attached) from briefly opening the window to quickly advance frames.

Trying to mitigate the problem, I added a circle of Red #25 gel filter to beef up the overall opacity of the window. I added flocking around the inside of the door with a hole cut for the window. I also added an overhang edge of flocking paper to the window cover so that it will seal more completely when closed. I don't think there are leak problems when the window is closed. When open, it is terrible. Why?

What is the big difference between the Holga and the Sputnik in this regard?

How is the light getting through the opaque paper backing?

From the shape of the leak, it doesn't look like a problem of light bouncing around. If I tape the developed film to the back of the camera and peek through from the shutter side (on bulb setting), the brightest center part of the streak lines up exactly with the exposure window. A minor leak will show up at the spot. A major leak will start there and radiate in NE and SW from that location. The film edges are clean. Also, if I really make sure to keep the window closed all the time, I don't get a leak.

How can I make this problem go away? Are there mitigation strategies I haven't considered?

I want to fix the problem and not be left to lurk around advancing frames in deepest shadow.

How is it that the Holga window is open all the time and doesn't have this problem?

Thanks!

That doesn't look like a leak from the red window, it looks like a leak from the bottom of the back. Sputniks are notoriously not light tight and suffer from severe internal reflections too.

Google before asking! Look at what this http://www.google.com/search?hl=en&...=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images
simple search turned up.

Dan,

Thanks for your tips. I have read all of these pages and have already extensively modified the camera at this point.

The interior bakelite has been flocked. All door seams (top and bottom) have had flocking stuffed into them. Baffles have been fabricated and installed. The left door where it meets the right door has been flocked. After each modification, this problem has remained unchanged while other leaks have been solved, contrast improved, etc.

The exposure window is my working theory at the moment. I tested exposing it open to the sun vs. closed to the sun. The open test shots had the effect shown above. The closed shots did not. Of course, it could still be something else.

It was a leak from the top of the back. More flocking, more covering. Solved the problem. Thank you.