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Michael Higgins

Prism Shutter

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Hi,

I recently picked up a 35mm hand-crank 'prism shutter (8sided) and I'm hoping to construct a simple 35mm camera. I generally work with destroying celluloid images, hand processing, vintage tech so I suppose for me any image is a good image. I'm not looking for complete perfection just some nice effects.

 

The shutter

http://cgi.ebay.ie/ws/eBayISAPI.dll?ViewItem&item=180702168485&ssPageName=STRK:MEWNX:IT

 

I've recently looked into the 'prism shutter' and have discovered its use mainly in high speed cameras.

http://www.photosonics.com/35mm_4bc_psi.htm

 

I'm wondering if anyone could possibly elaborate on the technicalities involved in the workings of such technology along with any additional parts that maybe required. It's very difficult to find any such info.

 

Regards,

Michael

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This kind of prism mechanism was most widely used for small screen viewing devices. But light goes both ways, so you can probably make a camera out of it. Play with a scrap of old release print to get an idea of what it does.

 

 

 

 

-- J.S.

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Yes it looks very similar to the prism in an old 35mm editing viewer that we have in our museum. The prism facets follow the film as it moves, so that each frame remains stable in the viewer before dissolving into the next.

 

It's the same principle at work (reversed) in high speed camera prisms, though the ones I've seen are smaller and coupled with a spinning, multi-segmented shutter.

 

To make a camera out of your nifty bit of treasure, you'd probably need a gate on the sprocket side to guide and hold the film at a consistent plane and a lens of some sort to focus through the prism. The smaller the lens aperture the less you need to worry about an exact focusing plane, so maybe just a pin hole would work? Otherwise a piece of tracing paper over the gate opening will let you see if you can get a focused image with a mounted lens. Without a shutter the prism facet will determine the frame, so you might get edges smearing or some other effect (not really sure!) but as John said, play around with some release print first and see how it works. Sounds like fun project!

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Thanks to all.

 

A Bronica 6x6 75mm lens is now temporarily mounted and infinity is showing up very well on tracing paper. Fun, next is to try and run a couple seconds of b/w through. Will keep you posted.

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