Sunday, May 1, 2011

Home Brew Focusing Helicoid Got Interchangeable Mounts

Home brew focusing helicoid with 55mm & M42 mount. Click to see larger.

I spent the long weekend last week getting my home brew focusing helicoid to become sort of modular.  Currently, it has a 55mm thread made out of a filter (without glass, of course), and I also made an M42 mount.  Together with the thinner 17-32mm helicoid that I bought, I can now use most of the odd lenses I have.  I am very glad that I have a large collection of step-up/step-down adapter rings that I got from the old Outlet Store.  They are now finally being utilized, especially the 55<-->52mm, 52mm <--> 49mm.  Perhaps I saw this coming :)

To make the lenses focus to infinity, I simply add/remove filter rings.  The advantage of this kind of adapters is that I can bring a few spare filter rings and add them on if I need to do some close up.

Next project is to make a focusing helicoid with aperture control, so that I can use the projection lenses and have control over depth of field.


  1. Great projects!

    I probably missed something but how do you attach the glassless filter ring to the lens? Also I see a number of M4/3s helicoids on ebay. One is a 17-31mm M42 > M52. Would that be the best one to modify? I also have an old Vivitar 2X Macro that I am not using. I mainly want to play with M39 enlarger lens but a flexible system would be desirable. What do you suggest?

  2. @Paul, I glued the filter rings on my lenses. I figured I will never used them again at they were originally intended, and they are not really worth much anyway. The 17-31mm M42-M52 is what I am using. Not the best quality focusing helicoid, but usable. In some cases, the Vivitar 2X focusing converter is too long for short focal lengths, for lenses shorter than 75mm. The 17-31mm is just barely enough to focus to infinity with a 50mm enlarging lens. For longer focal lengths, like 135mm, you will need to add extension tubes or lots of filter rings. Hope that helps.

  3. Exciting, I have a colection of old projectors and among those are a Leitz Prado but with a 400 mm. lens, that is the same projecting lens they used for their Episkop projectors. The Prado is a 35 mm. but most Episkopes project a halve A4 sheet image, still same lens are usedI wonder how the 400 mm. would perform. But even more how this 800 mm. ; placed over a 400 mm. ;
    Have you ever considered those types of projecting lenses ? btw I have a Nex5 myself, but newer dared try.

  4. @Percorell: I have a 200mm Leitz projection lens, but have not tried it yet. Typically, longer lenses are much easier to adapt but I don't use long lenses much, that's why I have not tried it yet.

  5. I understand, I just found the solution to attach a Nex to small Newtonian teleskopes, where the problem is to reach the focus point with the standard adaptors. Finaly I realised that a Nex - C-mount could be attached a C-Mount - 1,25" that is the tube that fit in those telescopes okular holder, and it is possible to use the focuser to gain focus. Trouble is that the standard adaptors are standard lens adaptors so it is difficult to profit from what I see as the greate advanteage about Nex, --- that it have no mirror and the chip is much closer the flange.

  6. M42-M52 are the best. There are some companies that sell the helicoids in various lengths: 12-17, 17-31, 35-90. Just search for "rainbow imaging" and you'll find the company. There was also a find a found a few minutes ago and there is a seller on eBay selling the M42-M42 helicoids with a low-profile NEX to M42 adapter (Auction 390551192653). I'm not affiliated with either hence no hot links. You can also use a 52mm filter step-up ring to go into the M42-M52 helicoid. It's not a direct fit as the helicoid will be M52x1 thread and the filter is M52x.75 but it's close enough to make the lens stay in. Another option, and I offer this very cautiously, and I provide no warranties expressed or implied. Is to use glue to make the threads. You file/sand the donor lens to provide cohesion for the glue, apply a non-stick coating (teflon, etc) to the helicoid, smear glue in and set in the lens. If you do it right you can unscrew the lens and you have a thread that fits. But, it's not as strong as metal and will chip more readily.

    I have yet to find M52x1 extension rings, yet.