Post by yashica1943 on Dec 21, 2015 5:38:38 GMT -5
When I bought my mint Voigtlander 28mm Skoparex with a QBM mount I didn't have a body to fit it on (I do now). I have a clean Canon EOS 3000n body which works, I cannot remember where that came from! I thought that it might be a good idea to look for an adapter, so I sent off to a Chinese seller on ebay for a new QBM to Eos unit at about £4. Wait about 10 days for it to arrive. When it does I find that I have to remove the 3 screws on the back of the lens and take the plate off to fit it. I don't want to do this and anyway in the meantime my really nice Rolleiflex SL35 has arrived.
So, the 'brain' starts ticking over and as I have a few M42 lenses stored away, I send off for a M42 to EOS adapter. This one arrives very quickly and just as quickly I find that none of my old lenses will focus to infinity using the new part. (Because of rear element to mirror distance!)
So then this genius decides to send off to China for a Pentax PK adapter. This time it takes ages to arrive. This morning it comes through the post. My nice 50mm SMC Pentax-M f 1.7 has a small part sticking out next to the aperture lever so that it will not fit the Canon body unless I cut the lever and part off. I am not going to spend any more time and money on this, so I will put the EOS body back in the storage where it came from. (I know that the EOS is a plastic camera, but I just wanted to try out some older lenses on it..)
Not an expert on Canon EOS, but the EOS to M42 should give infinity focus as the film to mount distance on the M42 is greater than the distance on the EOS, by 1.64mm, which if duplicated in the adapter, should mean it focuses correctly.
The reason for the plate change on the QBM mount is probably to do with the locking recess tab, which must be clear and in the right place, or you risk a permanently jammed on lens. I suspect the new ring has the correct register and locking release tab. There is no reason for this combination not to focus to infinity. I have another QBM to Micro 4/3 and that focuses perfectly.
Last Edit: Dec 21, 2015 16:51:16 GMT -5 by Stephen
Post by yashica1943 on Dec 21, 2015 13:36:00 GMT -5
Stephen, I have no problem with the QBM to EOS mount except that I am not going to devalue a mint Skoparex by removing the screws and probably marking them. The adapter has three screw holes in it and it completely replaces the plate. I am now going to use the lens on the Rolleiflex when I go somewhere interesting after the weather clears up.
The (my) M42 to EOS adapter has a flange at the rear which does not allow the rear element to go back far enough with the lenses that I have, to achieve focus at infinity.
The troubles with converter mounts are often not the mount converter itself, but what is going on to the sides and behind it in the original camera. With M4/3 to other makes there is little issue, as there is up to about an inch to play about with, but the EOS to M42 is wafer thin in comparison.
Not all M42 mounts are the same, the throat and mirror clearances vary a lot, especially types with extra levers or electrical contacts.
Fortunately as the Olympus Pen M 4/3 is so slim, the adaptors all work fine, as the spare space is generous, and no mirror worries.
It still has issues to the sides though with Leica thread, as the Leica Locking Knob, (early lenses), fouls most of the adaptors!
I think that the flange on the M42 adapter could be to depress the auto aperture pin on M42 lenses. I've used M42 lenses with no problems on Canon EOS cameras. Most of the M42 lenses I use are quite early ones with auto-manual switches which don't need the flange on the adapter. You can buy the adapters without the flange.
I have read about problems using some PK lenses with EOS adapters because of the protruding parts at the back. The Pentax M42 adapter for their K mount cameras fits inside the throat of the K mount. Any M42 adapter which fits on the surface of the K mount won't focus a lens to infinity.
I've not tried QBM lenses on any of my other cameras except on my Sony A7. I think that infinity focus can be a problem when using them with Canon EOS because of the thickness of the adaptor hence the replacement mount that some adapters include.
Another potential problem with full frame EOS cameras is the size of the mirror. It can foul on some non-Canon lenses if the rear of the lens protrudes too far back.
Post by yashica1943 on Dec 22, 2015 9:25:09 GMT -5
re The M42 adapter, I was wrong. I originally tried the converter on a Tessar from a Practika that I bought, but never actually used. I have now found that the lens, on camera or off will not focus past 5 metres towards infinity. Why, I do not know. The other lens was a 58mm Helios from a Zenit. Having tried it again, nothing is wrong with it. What I dd the first time I have no idea, so I now have Canon EOS with a Helios.