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09-03-2010, 09:05 AM   #1
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Trap focus modification - Takumar 135mm

I like to use the trap focus facility when I use my manual focus lenses, my Helios, Soligor's and a few others were easy to adapt with some sticky aluminium tape, but my Takumar 135mm is narrow and leaves the terminals on the K10 exposed.


So, after a bit of looking at it, I noticed a small recess at the back of the Takumar, and I thought that a ring might fit in there.


So I made one from some 1.5mm aluminium. The inside diameter is 51.6mm and the outside, which isn't critical, ended up at 66.5mm.


It's a 'good' fit, I made it so it doesn't have to be forced onto the lens and it will rotate when it's all mounted on the camera, but it's not loose.

In position, and working a treat. And it doesn't affect infinity focus at all, the register distance remains exactly the same.



Last edited by Lloydy; 04-08-2012 at 07:25 AM.
09-03-2010, 10:06 AM   #2
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Interesting, I have a similar recess on a 105 mm Vernon Edonar Preset lens on a T Mount.

A quick inspection of other M42 lenses shows most of them also have something similar.

This might be a nice thng to hav in a bag, or even permently attached to a lens.

One thing I note is that the auto manual switch can also occupy all or part of this space
09-03-2010, 04:05 PM   #3
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the auto - manual switch is no problem at all with this Takumar.

Sadly this ring doesn't work for any of the other lenses that I'd like to use with trap focus, My industar 50-2 falls right through this ring!
09-03-2010, 04:52 PM   #4
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But that's k mount.

I never noticed this on my M42, although I wasn't really paying attention. Plus, I'm too lazy to check it now.

09-04-2010, 01:59 AM   #5
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No, it's M42 with a non genuine Pentax adaptor - the horror!!!!
09-04-2010, 10:08 AM   #6
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Absolutely brilliant. You could easily sell those. I'd buy some!

Nice to see a fellow focus trapper. I adapt all of my Russian lenses by sanding off the paint,
adding an adapter (removing the locking mech.), and carefully drilling a small hole for the locking pin.

Could use one of your amazing rings for my vintage Vivitar 200mm.

09-04-2010, 02:20 PM   #7
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I'm an engineer by trade, and hobby, I love to make things. So when I saw what could be done I searched my workshop for something that I could use, but I didn't find anything so I made it.

The sort of thing I was looking for was a bearing shim, like you might find in a car wheel hub to set the bearing end float. I had plenty, but not the right size.

A quick Google however turned up this site -

Ondrives: Bearings - Ball Bearings - CPS - Precision Shim Washers - 52-56mm Bores

which has shims in all sizes, this page actually lists a 52mm i/d, 65mm o/d by 1.5mm thick shim, but they sell them by the hundred.
Over here I use local engineering suppliers that carry these kind of things and sell them singly.
So, if you can measure the size you need you might find your local engineering supplier becomes your friend.

I was also thinking that if a washer was used on a lens without the recess like the Takumar has, and it pushed the lens forward by maybe 1.5mm then it would lose infinity focus.
But the chances are that if you wanted to use focus trap you aren't focusing on infinity anyway. And the washer is removable when you want infinity.

problem solved, send all your donations to me!
09-06-2010, 02:56 PM - 1 Like   #8
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Thank you for the very useful information Lloydy.

PS. I love Mudplugga's photostream. Many, many great things!

09-07-2010, 10:22 AM   #9
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Thank you Jeff, I like to combine my two hobbies of making things and photography.
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