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Archive 2014 · Adapting a Tair-11 m39 lens to Canon body

  
 
reddtekk
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p.1 #1 · p.1 #1 · Adapting a Tair-11 m39 lens to Canon body


Greetings folks,

I've decided to do a quick write-up on my project of adapting my Tair-11 133mm f2.8 lens to be used on my Canon camera body.

m39 lenses are easy to fit to the m42 adapters commonly available on eBay using an m39-m42 threaded adapter ring. The issue is that the focal plane (at least in the case of my lens) is slightly closer on the m39 lens than standard Pentax m42 lenses. This results in a slight miss of infinity focus.

I obtained a reasonably good copy of the Tair-11 lens (occasionally referred to by some folks as the "bokeh monster") from an eBay seller in Bulgaria. I was intrigued by the bright nickel plating on the lens and the 20 blade aperture (which forms a near perfect circle from f/2.8 through to f/22). It's a beautiful prime, tack sharp through all aperture settings, fast enough to use handheld in many conditions, and a great focal length for stealth portraits, where you're so far from your subject that they don't realize that you're taking their picture. I put the lens on a Canon crop body (initially a 350D and now a 650D) using the m39-m42 adapter that the seller supplied with the lens and a cheap chipless m42 adapter. That infinity focus issue nagged at me though, and I quickly desired a solution.

So I did some searching. Somewhere on some forum (a couple years ago) I found a thread indicating what the focal plane of that lens was. It wasn't far off from the m42 focal plane and was still further than the Canon EOS focal plane so I decided to take the adapter to the metal lathe. Simply facing off a patch near the center of the m42 adapter ring provided the desired results, and I'm proud to say that I can now achieve infinity focus using this great lens.

Measurements are as follows:

I spot-faced the adapter down 0.030" from the original surface. Since there is a 2.122" diameter step in the Canon adapter on the opposite (male Canon EF mount) side, I kept as far as possible to the inside of the step to avoid making too thin a section. I made this diameter JUST big enough to clear my lens barrel, which was 2.055". Even if you over-step this or face the whole thing down to accommodate a larger OD lens, the adapter is 0.052" thick so you'll have 0.022" of flange thickness left. I'd be a little worried about distorting it if the lens were heavier, but my example is pretty small so I'm not concerned about it.

Overall I'm very happy with this. The lens is a little flare-prone since my example has a little bubble in the glass of the front element, but I'm really happy with the appearance of the photos I've gotten with it.

Hope I have been able to help someone.






May 25, 2014 at 12:15 PM
freaklikeme
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p.1 #2 · p.1 #2 · Adapting a Tair-11 m39 lens to Canon body


Hi, reddtekk, and welcome to the Alt Forum. I appreciate you posting, but I don't think you can call something a "bokeh monster" without some shots from it to back it up. Just my (not so serious) opinion.


May 25, 2014 at 10:45 PM
killersnowman
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p.1 #3 · p.1 #3 · Adapting a Tair-11 m39 lens to Canon body


ditto what freaklikeme said...

lets see what the bokeh monster can do =)



May 25, 2014 at 11:14 PM
reddtekk
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p.1 #4 · p.1 #4 · Adapting a Tair-11 m39 lens to Canon body


freaklikeme wrote:
Hi, reddtekk, and welcome to the Alt Forum. I appreciate you posting, but I don't think you can call something a "bokeh monster" without some shots from it to back it up. Just my (not so serious) opinion.


Gotcha folks.

I'm leaving for the Memorial Day parade with the lens.

Let's see what I can produce. If I don't get anything I like I'll fire up the ol' NAS computer and see what I've got stored there. I have one in mind that I shot of my daughter a few years back but I'm pressed to remember the date.

I'll update soon, thanks for looking.



May 26, 2014 at 08:47 AM
reddtekk
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p.1 #5 · p.1 #5 · Adapting a Tair-11 m39 lens to Canon body


Ok I'm back.

I've got six photos in the following link:

Click Here

The first three are photos of the setup - lens and adapter.

The latter three are taken with it. I intended to set all three with open aperture. The aperture ring might have crept closed a little on the photo of my youngest - but for the other two I set the stop to 2.8 to keep it from moving. This lens has a double ring for the aperture - one drives the blades and the other is a stop with detentes at the various f stop positions. Focus wide open then turn 'till it stops if stopping back.

The one thing I can speak of critically of the lens is that the focus ring rotates through about 350 deg. to go from 1.2 (approx.) meters to infinity. It helps for that precise adjustment of focus but can be a nuisance for switching from a distant target to a close one.

I'm particularly happy with the photo of the angel with the columbine and snow drops in the background.

These are raw, straight from the camera.

Enjoy.



May 26, 2014 at 06:21 PM
freaklikeme
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p.1 #6 · p.1 #6 · Adapting a Tair-11 m39 lens to Canon body


Thanks, redd. Those look great. The statue shot's my favorite of the three as well.


May 26, 2014 at 06:34 PM





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