Q about Nikon AI lens on Canon EOS
I've been hearing for years that with a suitable mount adapter, you can use Nikon manual-focus lenses on Canon EOS cameras. In theory it seems simple enough, since there is no electrical connection to the lens, Canon's flange distance is less than Nikon's, and Canon's throat is wider than Nikon's. But devils often lurk in details...
I recently decided to experiment with this after reading about the Nikkor AI 20mm f/4 lens, which was produced for only one year (from sometime in 1977 into January 1978). It was one of Galen Rowell's favorite lenses, and Ken Rockwell calls it the best wide-angle lens for film cameras (and presumably for full-frame digital as well if you don't mind giving up AF). So I ordered a Fotodiox Pro Nikon F to Canon EOS adapter, and I found (to my surprise) two of these lenses for sale: one at Adorama for $399, and one in an eBay auction from a dealer in Vancouver with 99%+ positive feedback. Both lenses looked to be in excellent condition. I won the one on eBay for significantly less than Adorama was asking for their copy. Here's a pic:
To make a long story short, everything came in the mail and the lens and the adapter both seem fine. BUT. I have three Canon cameras in the house: an old EOS 100 Elan film camera, a 5D Mark II, and a Rebel XSi. The adapter, by itself, fits fine on all three cameras, and the lens fits fine on the adapter, but the adapter with the lens on it only mounts on two of my three cameras. Naturally the one where it doesn't work is the one I really wanted to use this lens on, the 5D Mark II. It almost fits, but not quite; it doesn't fully seat along the bottom. This isn't an EF vs. EF-S problem, since the Elan is a full-frame film camera and predates EF-S by over a decade anyway.
Having inspected everything closely, I think the problem has to do with a little piece of curved black metal on the back of the lens. Here's a pic of the nether end:
You can see that there's a raised ring of black metal inside the mounting ring, and part of that raised ring (along the bottom of the lens, toward the far side of this picture) is raised even higher, forming a curving tab. I think this tab is bumping into the black inner body of my 5D Mark II just above the row of electrical contacts for the lens mount.
Eyeballing the 5D Mark II and the other cameras, the differences are subtle. It's not obvious why it bumps on this camera and not the others, but the 5D2 must provide just a little less space behind the lens mount. With EF lenses this wouldn't matter, but I don't imagine the 5D2's design was validated against Nikkor lenses during the development stage.
So I have a few questions for Nikon experts:
Why is that raised tab there? What does it do?
I've seen pictures of other Nikkor lenses and that part seems different on each of them, so I'm not sure if this problem means that NO Nikkor lens will fit on a 5D2, or if some will and some won't, depending on the size and placement of the tab. Any informed opinions out there? Any good rules of thumb to predict which ones would work?
Would it harm the lens' functionality on Nikon cameras if the tab were carefully filed down by about a millimeter to allow me to use it on my 5D2? I'm sure that would ruin the lens as a collector's item, but it's no worse than a home AI job -- as long as the lens still works right on Nikon cameras.
Does anyone know what kind of metal that part is, and what sort of file would be required to take it down a bit?
Obviously the rear element would have to be protected if I were going to do this. I'd probably gently tape one or more cotton balls over the glass (unless someone's got a better idea).
Thanks for any helpful advice or info anyone has. I'd really like to be able to use this lens; I'm curious to compare its images to those from my EF 17-40mm f/4L USM. I'm not afraid of manual focus and in any case you don't have to try very hard to focus a 20mm lens due to the short hyperfocal distance.
I recently decided to experiment with this after reading about the Nikkor AI 20mm f/4 lens, which was produced for only one year (from sometime in 1977 into January 1978). It was one of Galen Rowell's favorite lenses, and Ken Rockwell calls it the best wide-angle lens for film cameras (and presumably for full-frame digital as well if you don't mind giving up AF). So I ordered a Fotodiox Pro Nikon F to Canon EOS adapter, and I found (to my surprise) two of these lenses for sale: one at Adorama for $399, and one in an eBay auction from a dealer in Vancouver with 99%+ positive feedback. Both lenses looked to be in excellent condition. I won the one on eBay for significantly less than Adorama was asking for their copy. Here's a pic:
To make a long story short, everything came in the mail and the lens and the adapter both seem fine. BUT. I have three Canon cameras in the house: an old EOS 100 Elan film camera, a 5D Mark II, and a Rebel XSi. The adapter, by itself, fits fine on all three cameras, and the lens fits fine on the adapter, but the adapter with the lens on it only mounts on two of my three cameras. Naturally the one where it doesn't work is the one I really wanted to use this lens on, the 5D Mark II. It almost fits, but not quite; it doesn't fully seat along the bottom. This isn't an EF vs. EF-S problem, since the Elan is a full-frame film camera and predates EF-S by over a decade anyway.
Having inspected everything closely, I think the problem has to do with a little piece of curved black metal on the back of the lens. Here's a pic of the nether end:
You can see that there's a raised ring of black metal inside the mounting ring, and part of that raised ring (along the bottom of the lens, toward the far side of this picture) is raised even higher, forming a curving tab. I think this tab is bumping into the black inner body of my 5D Mark II just above the row of electrical contacts for the lens mount.
Eyeballing the 5D Mark II and the other cameras, the differences are subtle. It's not obvious why it bumps on this camera and not the others, but the 5D2 must provide just a little less space behind the lens mount. With EF lenses this wouldn't matter, but I don't imagine the 5D2's design was validated against Nikkor lenses during the development stage.
So I have a few questions for Nikon experts:
Why is that raised tab there? What does it do?
I've seen pictures of other Nikkor lenses and that part seems different on each of them, so I'm not sure if this problem means that NO Nikkor lens will fit on a 5D2, or if some will and some won't, depending on the size and placement of the tab. Any informed opinions out there? Any good rules of thumb to predict which ones would work?
Would it harm the lens' functionality on Nikon cameras if the tab were carefully filed down by about a millimeter to allow me to use it on my 5D2? I'm sure that would ruin the lens as a collector's item, but it's no worse than a home AI job -- as long as the lens still works right on Nikon cameras.
Does anyone know what kind of metal that part is, and what sort of file would be required to take it down a bit?
Obviously the rear element would have to be protected if I were going to do this. I'd probably gently tape one or more cotton balls over the glass (unless someone's got a better idea).
Thanks for any helpful advice or info anyone has. I'd really like to be able to use this lens; I'm curious to compare its images to those from my EF 17-40mm f/4L USM. I'm not afraid of manual focus and in any case you don't have to try very hard to focus a 20mm lens due to the short hyperfocal distance.
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Comments
While I do believe that you can completely eliminate the tab if you want, without affecting the basic mechanical or optical properties of the lens, you might try to find a donor lens to harvest the rear bezel and just replace the rear bezel on the Nikkor 20mm with the rear bezel from the donor lens. If you can find a suitable replacement rear bezel, that also leaves you free to revert the lens if you want to later.
Be extremely careful as the protruding rear element may still not clear the mirror and either the mirror or rear lens element (or both) may be damaged. I cannot find any written documentation saying what bodies that lens was safe to use on.
You may wonder how even shorter focal length lenses are safely mounted onto a FF body? The lens designers/manufacturers use an "optic relay" to provide a longer distance between the lens elements and the focal plane, preventing any mechanical interference.
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Still, I suppose one comparatively safe experiment would be to recharge the battery in my Elan and see if I can take a picture (even without film) without anything going wrong. Damaging the Elan would bother me a lot less than damaging the 5D2.
The donor lens idea is good, but I have no idea what other Nikkor models would be compatible both with the 5D2 and the physical construction of the Nikkor 20mm f/4. I suppose another lens of the same diameter would be a good guess, but who knows if the bezels would be similar enough to swap?
When I can find the time, I'll take the lens to a hardware store and see if anyone can recommend a suitable file.
Got bored with digital and went back to film.
That's great.
I've read where even 3rd party lenses and damaged lenses were used for that purpose. Yes, it takes a lot of exploration. I do wonder if that piece is just a simple bezel that may be removed without affecting the lens function. Looking at your image it's hard to tell.
If you do proceed with physical modification, it would be best to remove the part from the lens. Barring that, covering all of the other parts with a low-tack tape and plastic is generally what I have done (in similar projects.) If any of the tape adhesive gets left behind, a little lens cleaning alcohol swab generally removes the gunk.
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Thanks; I've signed up there. I found an existing thread where people are sharing information about using different manual-focus lenses on the 5D II, which is just what I need.
Got bored with digital and went back to film.
Good. I found the same thread the other week when I ordered my adapter too. I noticed what you mean about the lack of room in the bottom of the 5DMK2, it really is close to the flange. Let me know how that lens works out~!
I went to a local hardware store this morning and bought a small metal file with a triangular cross-section. Back home, I covered the rear lens element with a few layers of surgical gauze, held down at the sides by two fingers of my left hand. With my right hand, I carefully filed the metal tab down for several minutes. When it looked good, I cleaned away the metal dust, cleaned the back of the lens with a Nikon Lens Pen, and tried mounting it in my 5D Mark II. It fit! So I took it back off and filed off a little more metal just to be safe, cleaned it again, and tried taking a few pictures. Here's one:
Canon EOS 5D Mark II
Nikkor AI 20mm f/4 (1977)
1/320 sec. at f/4, ISO 100
Now to buy more ancient lenses at bargain prices...
Got bored with digital and went back to film.
Moderator of the Cameras and Accessories forums