Thanks Dan, I will print your diary and read it.
I think I had better make a more formal "lens bench", until now I have just been hand holding an old book-end with white paper.
I might add some vee blocks etc and a 6X9 gg screen and a Slik tripod mount so I can test things more accurately, using what I have here.
Do you have an access to a full machine shop? Other than lathe, what was used? A mill? I'm very interested in finding out more about how the back mates the body and how they are held together. It'd be great if you can share that part. I'm very impressed.
Great question T^ I too wanna learn the mechanics Wombat....I dream one day of a little machine shop and a darkroom....gotta plan early:)
Hi TK, and zsas,( and AGX who asked similar by pm)
Thanks for the queries.
I see there are more DIY projects of LF in wood. MF in metal is not so common and requires more accuracy.
Lathe is a South Bend model 9A which was delivered to its original owner in Detroit in 1939.
I acquired it in 2011 as second owner with a comprehensive set of tooling and attachments.
That included a small machinist's surface plate which is ideal for camera measurements.
The lathe was used in the original owner's residence as a hobby lathe and it is in excellent condition.
On it I have made, from solid Al 6031 billet, lens adaptors from Micro 4/3 up to the Pentax 6X7 bayonet and threaded adaptors too.
I have just purchased (from Australia, for reasons rather too lengthy to explain here) a compound gear set to allow machining of metric camera threads.
The Leica M39 mount is actually a 39mm Whitworth thread with 26 Turns Per Inch , so I purchased a set or Whitworth threading tools from UK.
The "elementary" mill drill is a work in progress.
It is based on a Delta Shopmaster DP200 pedestal drill purchased new in about 2005.
I recently added a generic cast iron "Made In China" XY table to convert the drill for limited milling duty.
There are issues in doing such a conversion, including safety, which are documented in the machinists' fora (forums) perhaps with varying degrees of veracity.
I have made some weldments (in mild steel by oxy acetylene bronze welding) to bolster the rigidity of the thing and just today (when I got tired of yard work) I spent a couple of hours on what I hope is the final weldment to make the head much more rigid. I reckon I have a few more sessions to go on that project.
I am aiming for a consistent TIR of 0.05 mm (0.002 inch) on say, a 6X9 frame in aluminum.
I am using 4 fluted spiral side/end milling cutters in range 4 ~ 7mm, dry on Al.
To answer your question about the back more specifically:
The Graflex backs here are an RH/8 and a Singer RH/10. Both at least 30 years old and well used.
Both have the pin rollers that are documented as necessary for the modern 120 film (I have no experience on this)
I measured carefully and decided that the distance from the emulsion side of the film (contacting the pin rollers) to the contacting front of the back
was 5.080 mm , 0.200 inch, considering wear.
here are my actual measurements in the 4 corners [inch]:
RH/8 0.180, 0.190, 0.202, 0.200
RH/10 0.175, 0.191, 0.179, 0.180
I assumed that the RH/10 was a bit more worn than the RH/8, also my calipers pull the pin rollers to the front of their spindles which the film may not do.
The Graflex Singer back is bolted to the Eddystone body by 4 clamp plates which were actually quite difficult to make first time. Next time will be easier.
You can see them on the rear view in the op link.
I have a question for Dan Fromm, if you are around.
I finally have my metric thread cutting gears. They are much traveled, made in Australia which metricated in 1966, in my baggage from Australia through South America countries to Michigan.
Query, As I think Dan can answer - if worthwhile and save me going into a dead end here.
If I machine an adaptor to orient the Rodenstock Rogonar-S 1:2.8 50mm M39 thread, to the year 1957 Prontor-SVS shutter, the distance from the rear element (lens thread end) to the iris will be approx 15mm.
Now I can make the shutter face the real world, and the nose of the Rogonar will point to the film; I can adapt that assembly to the Graflex lensboard of my home brew camera. That is, the lens will be inside the camera, and the shutter will be on the outside of the lens board. Of course I can place the longitudinal register for infinity focus.
What will be the approximate image circle?
Will the distance to the shutter/iris affect sharpness too much?
Edit Oh, I realize I can hold the iris of the shutter open and use the stop in the lens!
But my queries still stand....
Wandering Wombat, what are you trying to accomplish?
If you want to use the Rodagon as a wide angle lens on 2x3, give the idea up. It is made to cover somewhat less than 43 mm at infinity.
Inaccessible lens behind shutter is a recipe for frustration. There's nothing wrong with putting a lens behind the shutter, if the lens is in barrel and its diaphragm ring is accessible.
I've seen only one semi-clean solution to putting the lens behind the shutter and inside the camera; it was implemented for the Polaroid MP-4 system and has led some innocents to the mistaken conclusion that the Polaroid MP-4 shutter (so badged) has a diaphragm. It doesn't, but some have a device for operating the diaphragm of a barrel lens behind the shutter.
Its time for you to study the Alpa 12 and Alpa's further extensions of the 12 idea. Lovely camera, if much too expensive for most of us, and not as far from your idea as one might think.
Oh yes, Alpa 12 is my kind of camera !
So the Rogonar 50mm is no good.
I know from using this lens on a digital sensor that it is very sharp in range f/8 to rf/11 , whereas the Omagaron 1:4.5 90mm I have here is not so sharp across the plane and anyway i need a shorter lens.
My next step is to make a lens bench so I can experiment to find a little lens less than 90mm to do what i indicated in post 25, mounted behind the lens board and that Prontor svs shutter.
I am interested in making a Crayford focuser out of billet alloy, to be mounted in a Graflex lens board. I think I can do it, I suppose the trick will be how to keep it light sealed
Thanks for your help.
Wombat, you're on the slippery slope. There;s a law of nature to the effect that there are no inexpensive wide angle lenses for formats larger than 35 mm still.
Suggest you visit www.schneideroptics.com, use the info tab to find their data on older lenses, and look at their short lenses' flange-focal distances. Then redesign y'r box (shorter! That's the Alpa trick) to allow you to use one of them, 47 SA, for example.
You're falling into a trap I'm familiar with. Have a cute idea based on a very inexpensive piece of found equipment, start thinking about what more can be done, and get fixated on using the piece of found equipment instead of thinking about what doing the what more really requires. Been there, done that, don't recommend it. Open your little marsupial mind.
But... But... But...
I can put that Graflex lens board where ever i want in relation to the film plane.
The Eddystone diecast boxes only cost $15 or so and are available in all sorts of dimensions
What about just using a 75mm achromatic doublet .. behind the Prontor and on a Crayford?
I have been reading up on geometric optics but not up to speed on how to calculate image circle
100% home brew, that is what I am aiming for.
And good image quality too?
Originally Posted by wombat2go
Teasing aside, what you want to do isn't what I'd do, but if that's what you want, why not? Your objectives, your resources including time.