M42 to Canon EF adapter, can't focus past ~3m

[nameBrandon]

Hey gang! I'm hoping you smart people can help me with this issue..

I just snagged a pristine Takumar 50 1.4 (S-M-C) and tried to get it on my Canon 5DII, and it mounts via M42 adapter, but when I try and focus past ~3 meters, it starts to become very difficult to turn the focusing ring.

Without the adapter, the focus ring turns just fine. I should point out that as long as the adapter is present, the focus ring is difficult to turn after ~3m. It makes no difference if the lens is mounted on the camera, or not. Manual / Auto switch position doesn't seem to have an impact on this issue.

I have two M42 to EF adapters, both do the same thing. However, when I put either adapter on my Takumar SMC 55mm 1.8, the focus ring turns without any problems.

So I assume there's some slight difference between my 55mm 1.8 and the 50mm 1.4.

Can someone help me understand what's going on, and if possible, link me to the correct adapter (preferably with AF chip.. )..

Thanks!

[visualopsins]

There is some mechanical interference between lens and adapter as lens is focused past ~3m. Perhaps the hole in the adapter is too small for the rear of the lens to go through...

Is adapter flanged or not?

[nameBrandon]

Both adapters are flanged.. makes sense, so I probably just need a non-flanged adapter?

edit -
actually, I looked a bit closer, and it appears there's a plastic piece that sticks up out of the rear of the lens. When the adapter is on, it bends that plastic piece forward. The plastic piece then gets in the way of the lens mechanism that extrudes when focusing at longer distances.

So I think the flange is actually pushing on the plastic piece, which is in turn pushing on the moving part of the lens as it extends outwards.

So now just to find a non-flanged adapter with chip.. do they make one? I'm not sure if there's enough room to put the chip w/o an flange?

[calvin83]

[nameBrandon]

Thanks! I found one at Fotodiox, just placed my order.

[MTHall]

There is an issue with fitting some Pentax Takumars to M42 adapters. There are some of these lenses that were intended to fit specific Penrax models that had extra facilities fitted, some were to do with full aperture metering and had an index protruding off the back of the lens base and another that connects to the aperture mechanics that also protrudes some 3mm from the base's throat. If you examine the rear of the lens these features are quite obvious and if there is dificulty in operating this lens because of the fitted adapter, the lens could suffer damage! (Maybe the adapter too!). Later M42 Pentaxes sported a host of extra features not found on other M42 cameras, Pentax pushed the boundaries of this mounting to the maximum, before launching the PK bayonet mount series of cameras. I have a Pentax M42 Takumar f2/55 SMC lens that is of this series. Looking at the rear of this lens: bottom of mount is normal push pin aperture, aprox 85deg right a square index peg, 5deg further on the mount face is a small sprung pin, at the top of the mount protrudes the aperture's meter operating lever**.

** this part is what may be causing the focus to jam on your lens!! When the lens is being `screwed into' the adapter, it is common to unscrew the focus to `close up', if as you mount the lens to the adapter this forces this operating lever inwards only a little, then the focus will jam against it as you screw the focus back towards infinity. Am I making sense? If so, I hope it helps you.
VBR

[MTHall]

http://forum.mflenses.com/userpix/201211/6221_TwoTakumars_1.jpg

On the left is a Takumar f2.8/105 with a bog standard M42 mount, on the right is a f2/55 Takumar M42 with added extras, as described in my previous post. There is no known problem with the M42 extra being fitted into most M42 cameras. But it has to be pointed out, that Pentax weren't the only camera manufacturer who extended the M42 platform. Mamiya and Fuji did too with several of their 35mm slr's. As soon as TTL hit the high st., there were attempts by competing manufacturers to go for TTL open aperture. Because there stemmed from this, compatibility problems between different M42 cameras and lenses, Pentax introduced the PK Bayonet mount series and Mamiya went back to MF cameras.

[peterqd]

I had this problem with my Super-Tak 1.4/50. I use a plain adapter without the flange for this lens and use the A-M switch to stop down.

[MTHall]

I can see the problem, Why does it need to cover the back of the lens so? There are lenses with larger rear elements too, as well as the issues I pointed out earlier. How much of that flange is necessary and can it be machined away?

[visualopsins]

[peterqd]

[nameBrandon]

Just a follow up to this, the flange-less adapter worked fine. No more issue with the little level being bent forward causing the retracting lens piece to rub. If it matters, this lens had a Honeywell lens cap, so it probably was a later lens.

Thanks everyone