Procedure: Reducing internal reflections

Thanks to: David Burder (copy provided by Stephen Spicer)

Disclaimer: This data is provided for informational purposes only. You must assess your ability to perform the operations described. Neither the individual contributor nor Rocky Mountain Memories assumes any responsibility for damage you may inflict on your camera by following these directions.


David Burder, August 1987

Whilst the vast majority of 35mm stereo cameras have a 5 perforation format (24x23), the Verascope F40 and the Bel plasca are the two most common cameras offering the wider 7 perf (24x28) film area.

Both cameras have their own respective pros and cons: for example, the Belplasca gives crisp and contrasty images from its Tessar lenses, but lacks a range-finder, feels cheap and has no flash shoe, only a standard co-ax socket on the cameras bottom!. In comparison the F40 looks and feels really solid, has an excellent range-finder, a standard cold flash shoe on the top plate but a pair of totally non-standard flash sockets. The only snag I have found is that the results were pretty appalling; the images were gutless, soft and lacking contrast. Only with flash did the pictures start to look decent. Having owned three of these cameras, I decided that something should be done to achieve better results.

Jumping in at the deep end, I removed the French Flor lenses and replaced them with 40mm Rollei Triotars from the baby Rollei compact camera - the results were better but not good enough so I started to look around for a pair of Tessars or Sonnars from the more expensive models. Meanwhile, I found a pair of Olympus 4 element lenses and fitted these. But still the results were not as bright as those of the Belplasca so I decided to see if there is something inherently wrong about the camera itself. There is! The whole design of the camera interior is bound to give appalling flare, thereby reducing contrast and generally degrading the image. The shape of the body cavity forces all non-image forming rays back onto the film plane destroying the quality of the picture. To prove how bad this is, just put the camera on B and look through the back at a strong light.

The solution was not difficult; firstly I machined an exactly matching pair of lens hoods; rectangular in shape to stop all unwanted light from entering the camera. These were designed to work 100% efficiently when focused at maximum close up and maximum aperture, even though this means they became a bit less efficient as aperture and focus were reduced.

The second part of the solution, which is also not difficult for the handyman, is to remove the solid aluminium film plane panel (5 screws) and file away the sloping channels until the camber angle is reversed. At the same time the window can be slightly opened up to give a slightly deeper image area on the film, always useful when mounting. The surface should now be painted matte black. When the film plane channel is removed, various bits and pieces will fall out but these can be happily discarded as they are only the dangerous metal slide which is used to blank off the right frame when doing sequentials (The F40 can be used to expose 20 stereo pairs or 40 mono photos on a 36 exp roll - SS). However, it will still be necessary to ensure that the control knob on the top plate is pointed on the stereo (not mono) position for the 1-3-1-3 wind on system to work correctly.

David Burder, August 1987

Rocky Mountain
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