DIY Medium Format camera
Below is a description of the camera body that I completed in March 2013.
I call this camera "WomTak1" and I am starting on 'WomTak2" which, if it succeeds, will have an internal electronically timed shutter for use with the wide angle Takumar 6X7 lenses
The lens is a "Super-Multi-Coated Takumar/6X7 1:2.8/90" with the leaf shutter.
The camera body is based on an Eddystone die-cast aluminum box.
These boxes are used in electronics for radio frequency shielding. They are accurately made and the walls are thick enough for machining.
The box lid has a ridge inside that forms a light tight seal.
Using the Eddystone box saved a lot of work in this project.
A square with a groove for light seals was milled in the bottom of the box to form the mount for the lens board.
The lens board of 2 laminated plates of 6031 aluminum is somewhat based on the Graflex 4x5 lens board.
A P6X7 bayonet mount was turned in the lens board using the lathe.
The back is clamped to the lid which is machined with the film gate and a light seal.
On Graflex cameras, the back is held with quick release clamp slides, but on this camera the clamps are bolted.
The Graflex (Singer) RH/10 roll-film back contains a truck for 120 film giving 10 exposures of film gate size 57.4 by 67.5 mm.
Also it will take the truck for an RH/8 back, giving 8 exposures for a total of 18 shots if the spare truck is loaded and taken in the camera bag.
The published register for Pentax 6X7 is 84.95mm
The estimated register of this camera is 85.09mm at 25 C and 84.89mm at -10 Celsius
The TIR of the lens mount parallelism was measured as 0.05mm. However that does not include the Graflex back.
A 6X7 ground glass was made to fit against the film slides.
The camera was checked with a loupe at 4 metre and infinity and the lens scales were found to accurate.
The bottom of the camera contains a tripod mount machined in brass and threaded 1/4_20 into a blind hole.
The side has a stainless steel industrial handle angled for a personal grip.
Tho top has 4 bolts for optional viewfinders.
The present viewfinder is very simple, the lenses were chosen by flipping lens elements in the junk box until an arrangement of 2 meniscus lenses from the front of an old zoom were placed to give about 3+ diopter (focal length 300mm or so).
The eye cup is much larger than on a normal camera
The viewfinder has significant barrel distortion which is actually an aid in centering the image.
The spirit level is easily visible in the bottom of the vf with the help of the lenses.
The camera with film , back and lens weighs 1.96 kg (4 lb 6 oz)
There is presently no rangefinder or meter, so the Pentax MX with the SMC Pentax-M 1:2.8~4 40~80mm is taken in a compartment in the camera bag
The zoom makes a good rangefinder at 80mm and being of wider aperture than an ordinary zoom, has a bright image in the MX viewfinder.
The roll film back has a dark slide which is not really necessary as the leaf shutter is normally closed.
photos with the MX alongside
with AF360 Flash
Here are some photos taken by the new camera
These shots on Fuji 400 were focussed just by estimating distances and using the DOF scales on the lens.
In use this camera is much easier to use hand held than the Speed Graphic, it is only necessary to remember to wind the film after each shot.