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Lens Issues on a DeVry "Lunchbox" Camera


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#1 Aaron Martin (TX)

Aaron Martin (TX)
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Posted 12 September 2008 - 03:42 PM

Hello,

I recently purchased a 35mm DeVry camera. The camera itself works great, the spring is really strong and the hand cranking mechanism works very smoothly. The problem I am having is with the lens on this camera.

My camera arrived with an f3.5 50mm Wollensak lens, which I believe is one of the standard lenses that DeVry cameras came with. The lens housing is in remarkable shape for being 80 years old, but its the optics that I am worried about. The aperture leaves and the focus ring all work very well, but when I look through the funky little mirror/reflex finder (which is very clean and appears to have been replaced) on the side of the camera, the lens never seems to bring anything into focus on the surface of the mirror, except when I back some distance away from the viewfinder port. Even then when I change the focus on the lens the focus on the image does not appear to change. I can also clearly see the leaves of the aperture working when I change settings.

So, am I out of business with this lens? My guess is that either the camera or the lens are missing an element. My other guess is that the replaced mirror is sitting at the wrong angle. I have owned a DeVry before and I don't remember there being any glass or prisms in the camera itself. Frankly, that other camera was in bad shape and mirror/reflex finder was such a crusty mess that I never tried to use it.

My other issue with this camera is that the spring motor seems to run almost too well. Does anyone out there think one of these things could be hot-rodded into running at 24 fps?

Thanks in advance for your help. I'm happy to provide you with any more info if you think it will help in diagnosing this problem.


Aaron
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#2 David Venhaus

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Posted 12 September 2008 - 04:34 PM

The lens is supposed to focus the image on the film plane, not on the mirror behind. It needs to have film in the gate, for focusing, as how it was originally intended to be used. The camera was designed for b+w films (that lack Remjet or similar coatings) so the image could be seen through the emulsion on the base side, which the mirror will then reflect to the optional eyepiece. So you could use a short strip of a similar such modern undeveloped b+w film and insert it into the gate to check focus for lens testing.

As for the speed, you could just measure a length of some scrap film and run it through the camera, keeping time with a stop watch, then calculate what the speed is from those measurements. I have seen special modified versions that ran at 24fps, but most of the "lunchbox" ones, as far as I know, were originally built to run at 18fps. There is a governor mechanism inside the camera that regulates the speed of the movement but I don't personally know how to change it.
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#3 Sam Wells

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Posted 12 September 2008 - 06:08 PM

As for the speed, you could just measure a length of some scrap film and run it through the camera, keeping time with a stop watch,


Or film the stopwatch !

-Sam
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#4 Aaron Martin (TX)

Aaron Martin (TX)
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Posted 30 September 2008 - 02:49 PM

Thank you both very much for your responses.

Here's a another question: Is it possible that my lens is missing an element? Would that explain what I'm seeing?


Aaron
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