Re: Finding camera leaks

[P3D Joel Alpers <joel.alpers@xxxxxxxxxxx>]

Greg Erker wrote about this neat way of finding light leaks:

>   Load your camera with a roll of high speed film (at least 400)
> in a dark location. Close back and advance to about the 3rd
> frame (this is so that you have unexposed film on the take up
> spool).
> 
>   Go out in the sunlight or other bright location and hold the
> camera in various orientations so that the light strikes all
> possible leaking areas.  Take one photo with the camera, but
> underexpose by about 2 stops. Do not advance the film.

I modified this slightly in my testing; I covered one of the
lenses in the camera being tested - this allows you to see if
any light is leaking within the film chamber. Note that the
"do not advance" is critical. As Greg mentioned, I recently did
this test on a Sputnik which I thought had leaks at the image
film plane. To my surprise I found that the light leaks were
-not- there, but on the -sides- of the camera. Not advancing
the film gives you a great little "map" of where your light
leaks are coming from.
 
>   Go back to the dark location and rewind your film. Get the
> roll processed, specifying "Do Not Cut" . You can get it push
> processed, if desired, to help show the light leaks (or do it
> yourself if you process your own).
> 
>   Place the strip of developed film in the back of the camera,
> aligning the underexposed photo with the film gates. You now
> know the exact location of any light leaks.
> -----
> 
>   So if you are willing to waste/invest a roll of film, you can
> know where your camera leaks.

I recently did this test on a 35mm camera. I took a roll of P3200
36 exposure film into the darkroom, unrolled it, and re-rolled
it onto three "bulk loading" spools. That way I could run tests
on three cameras, which made for less film "waste".

Do this with B/W film and develop it yourself, and you have a
really quick, cheap way to find out exactly where your light
leaks are coming from. It works great!

Joel.


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