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.
Ok, so you've made a cute little camera that works with PX 67 lenses in leaf shutter. Its been a long time since I thought about that system, so please enlighten me. How many lenses in shutter does the system have?
Dan, There were two lenses of the Takumar (Pentax) 6X7 with leaf shutters. - the 90mm and 165mm.
The next camera i make will be similar, but with an internal shutter. That will allow use of the wide angle Takumars i have.
I have just purchased a Copal 495, it is a plate shutter with 45mm opening, powered by a solenoid.
I am about to set the shutter up on a lens bench and measure its performance with a phototransistor and oscilloscope.
I think I can modify it if necessary to speed it up by adding a closing solenoid. I suppose it will be OK if I can get a top speed of 1/100th to 1/125th out of it.
The Takumar 90mm leaf shutter has a speed range, with flash sync, from 1/30 to 1/500.
Hi wombat - I can't see your pics of the camera??? The pics you took with it, I can open....any ideas?
Regardless, congrats on your camera!
That's fantastic. I guess you zone focus with it and just use the viewfinder for composition?
Thanks for the reply. Have you considered making a shorter box (can you shorten an Eddystone box?) with a large, e.g., Compound #3 or larger or Ilex #4 or larger, leaf shutter in front of it with a PX 67 female mount attached to the shutter?
The obvious step beyond that, given my prejudices, would be to change the rear (stepped plate?) to hold a Mamiya Press "M Frame" (better in some ways, perhaps worse in others) or a 2x3 Graflok (worse in some ways, perhaps better in others) and to use, respectively, an S-shaped Mamiya Press roll holder or a Graflex roll holder. Mamiya Press roll holders are supposed to hold the film flatter than Graflex ones but I don't know where Mamiya ever offered a focusing panel for the M Frame. With a Graflok you'll have a focusing panel, will be able to compose through the lens.
A question. Why carry several inserts for your roll holder? They're not light tight, can't be carried safely loaded, and have to be in the shell before film can safely be advanced. Using an RH-8 insert in an RH-10 shell wastes film. If you can take an insert out, you can reload it and put it back in.
I have a little experience with a broad range of lenses (45/9 WA Dagor to 480/9 Apo-Nikkor) mounted in front of a Compur/Copal #1 shutter on 2x3 Graphics, have had no difficulties with vignetting and few difficulties, including one huge embarrassment, with loss of diaphragm control. Diaphragm control can be lost when the shutter's maximum aperture is smaller than the lens' exit pupil.
To be clear, I'm far from sure that a #1 won't give you vignetting because I don't know how far your lenses' exit pupils will be in front of the shutter. It works for me because my front-mounted lenses are always close to the shutter and the shutter is usually relatively far from the film plane. Not your situation, in general.
Good luck, keep on having fun,
Sorry that you can view some of the links but not others
Here is a link to the directory on box.com containing all the photos linked in the op.
Matt,Thanks and you are correct.
I have a plan to make a more elaborate viewfinder using an SMC Pentax 1:2 55mm ( a 35mm lens) , a ground glass screen, and a 45 degree erecting prism.
I have checked the taking lens and that lens with a tape in range 4 ~6 metre and their scales are accurate, so i would transfer the reading from the VF lens on to the taking lens.
That would allow more accurate focussing close up. Beyonds about 5 metre, my guess is fairly accurate especially above f/11 or so.
Standing ovation for you sir! And I honestly expected it to be ugly, but that is a thing of beauty. You know, another lens option for such a project would be the Koni-Omega lenses. They have shutters, and go down into wide angle.
Dan, Thanks for the comments and I copied them into a file so I can go through the suggestions.
I used the RH/10 back mainly due to cost, they are only about $75
The materials for the camera body are less than $30, and the older Takumar lenses are also available for less than $200 from KEH etc.
For next, version 2 body I have a big copal "495" shutter, it is on a phenolic plate, does not look like an ordinary shutter, I think it was intended for behind the lens.
I was happy to find that for $40 . The Takumar 6X7 wide angle lenses are retrofocal and have large diameter rear elements, hence I need a big shutter behind the lens.
To save loading the holder I have a lens bag that is light tight and wide enough to take the truck, so I can just changeover as necessary..
I also have a new Prontor shutter. I have ordered a metric screw cutting gear for my lathe.
The thought there is to do as you suggest and make a mini MF camera with a wide angle lens. For example I have a 50mm Rogonar-S enlarger lens.
I can machine the metric adaptors, and I was looking at the Crayford focusser for that idea.