Single element, uncoated, fixed aperture 50?

[rbiemer]

So, I have an Industar 61 that is broken: the aperture ring simply spins with out effecting the aperture. I suspect that the grub screws are broken. Not really worth fixing but I had another idea:
To replace the optics with a simple, uncoated lens and put a fixed aperture stop behind the lens.
What I'm thinking is that if I buy a 50mm nominal focal length lens from Edmund Scientific or Surplus Shed and put an f8 or f11 stop behind it that should get me enough depth of focus to cover most focus error? I don't have the skills to truly collimate a lens. If I'm patient, I should be able to get this thing put together fairly well; ideally with the front filter ring in place so I can get a hood on it. And/or filters--probably ND to try to get a usable shutter speed and fstop combination.
The I-61 lenses are sometimes marked as "50" and sometimes other lengths "52" or "53" I seem to remember seeing. The one I have is marked "50" but are they really all "50+"?
Seems like cheap fun to me!
Any suggestions, ideas, questions?
Rob

 

[Sonnar Brian]

I've done this before.

I would suggest going into the local thrift store and getting a "time/Life or Something" Plastic 35mm camera with the 50mm lens. Collimating is fairly easy. Take the optics out of the I-61. The mount is fairly close to 50mm. The rear light baffles pop out, and made a decent optics mount. You need to be relatively close, even at F8, but that is not hard. Get a plastic tube and some sand paper. Use a film strip and loupe at the film gate of the camera. File the homemade optics fixture until it is a decent focus.

 

[Merkin]

you could always buy a holga, either the mf or the 35mm one, chop off the lens and the part of the body the lens screws on to, cut a hole in a spare body cap, and glue the holga lens mechanism on to the body cap. you would have a fixed f11 or so lens in either 45mm or 65mm.

 

[rbiemer]

So, I want to end up with the "new" lens in the same place as the old one?
My local thrift/salvation army stores have been a bit scant for any kind of camera which was why I thought of Edmund or Surplus Shed. I looked at Surplus Shed's site and they have about 20 different "50" mm lenses, PCX, BCX, etc. Most seem to be coated but some are not and the price is about what I'd pay for one of the plastic cheapy cameras. And their's are glass.
I will see what is available this weekend, though.
Thanks, Brian, for your thoughts on this. Much appreciated.
Rob

 

[rbiemer]

Merkin, a good idea though with what the Holgas are costing lately, not quite so thrifty as I want to keep this idea.
Rob

 

[Sonnar Brian]

I found that the single-element lens, mounted on the light baffle, glued to the lens mount after removing the optics module, is at "about" the right place. A little filing or moving out one way or the other optimzied it. Mine came out RF coupled.

 

[rbiemer]

So, I got a small package of "50"mm lenses yesterday; two DCX, one PCX, and one PMN. After some experimenting, I found that one of the DCX lenses when simply taped to the lens mount, seems to be focusing fine. I put the assembly on my Bessa R, put that on a tripod and locked the shutter open. Checked focus near and far with a piece of ground glass at the film gate and a loupe.
This is what I'm going to mount the lens to:

Now I need to figure out the aperture. That opening is 27.66mm and with the lens taped in place, I got the meter of the R to read "correct" exposure as 1/1000 for ISO100. With my J-3 lens, to get a similar reading, I needed to set the lens to f1.5 . To get to somewhere around f11 I am going to place a disk with a small hole in it between the lens and the mount. Trial and error will suffice for this but I think I'll start with 4 or 5mm and see what shutter speed that gives me.
Run a short roll of film through this before I permanently attach any of it and see how things look. Adjust as needed, then epoxy it all together.
Once I get the lens and stop in place, a hood is next. Probably just a simple tube either painted flat black or lined with flocking paper.
Rob

 

[Sonnar Brian]

I used an aperture disk for one lens that I made similar to this. I made a holder so it could be changed. Allows experimenting with different shapes for Out Of Focus areas.

Have fun! Great use for an I61 Mount. What did you do with the I61 optics module? They go great on a J-8 Kiev mount.

 

[rbiemer]

All the other parts of the I61 are sitting on my desk, if you want them, Brian, you are welcome to them.
The changeable aperture idea is tempting but I want to keep this as simple as possible. And adding more "stuff" between the lens and the mount would mean using a different lens I think.
Rob

 

[johannielscom]

I love lens hacking too. I just now dug up a Petri 55mm f1.8 SLR lens, M42 mount. An Industar I-61 might arrive this afternoon, the FED-4 it is on I will probably marry to my 1953 J-8. If the I-63 turns out to be useless, I might fix the Petri to the lens mount, that Petri is very nice and not too big.

Nice little venture for a Friday afternoon.

Good luck on your hack, I'd like to see the results of and with it!

 

[rbiemer]

Yesterday in the mail I got back a bunch of processed and scanned film. Unfortunately two of the 15 rolls were not actually scanned; I got two lovely BLANK cds. 🙁 Of course one of those is the roll I shot with the lens I built. The negs look interesting but I've no way to share them here.:bang:
So those two rolls are going back to the lab and I will post some of my results once I get the scans.
Rob