Adapting a Lens (MF) Question

I can't seem to find my FD to EOS adapter, since it really doesn't make an FD lens usable, I probably tossed it in a pile of junk, and haven't located it yet, otherwise, I'd answer this question myself.

If you have an M42 lens, and you put an M42 to FD adapter on it, then an FD to EOS adapter (all with no optics), will it focus to infinity? M42 flange to focal plane is 45.5mm, FD flange to focal plane is 42mm, and EOS flange to focal plane is 44mm. I would think that the thicknesses of the two adapters would be too much to allow infinity focus, but I'm not sure.

I think it would work on a T2 Mount (55mm flange to FP), because there would be enough room to allow for both adapters.

Now, you're all probably saying to yourself, why not just use an M42 to EOS adapter (of which I have many)? It's not that easy in a very specific situation I'm up against. I have a Pentax/Takumar 500mm f/4.5 (which typically was available in M42 and Nikon mounts), but this one has an FD mount. The interesting thing about this lens, is that it was designed with interchangeable mounts. The lens itself is huge (440mm or 17+ inches), and weighs in at nearly 8lbs., but the mount is a small piece that bayonet mounts to the lens body. I'm thinking that the lens was designed with a long flange to FP distance, and you just bought the adapter you needed. I'm also thinking that even though the mount it has is FD, the focal plane is going to be much more than the normal 42mm for FD. The chances of finding an M42 or Nikon mount for it (which can be adapted) is about nil.

Attached is a couple of shots of the mounting piece, just because.

This side attaches (bayonet mount) to the lens body;

This does not look like a camera lens to me. More like an enlarger lens. Not worth the effort. There are a zillion M42 to EF adapters on eBay. In general when trying to adapt older lenses to EF avoid FD.

No, that's not the lens. That's only the mount adapter. It is an interchangeable mount. I'll get a pic of the lens with and without the mount up for you. The lens is the Takumar 500mm f/4.5. Pretty sure I said that in the OP.

Here's what the lens looks like (not my image, but the same lens): http://www.pentaxforum​s.com …_Takumar_Pentax​_500mm.jpg

My pictures above are of the very back section of the lens.

Sorry, guess the pix drew my attention away from the print. Tak 500 (an ok lens but not highly rated) should be either M42 or P/K mount, both have simple EF adapters.

No... The lens was available in M42 mount, or Nikon mount (I've been able to confirm that), and ot appears as though it was also available with an FD mount. This is the first version (c. 1967), and the base option was the M42.

With that said, do you think that the Flange to Focal Plane would be long enough to allow for use with an FD>EF adapter? I realize it's only a guess at this point.

You need to get FD out of your mind.

KirkS518 wrote in post #16791124
No... The lens was available in M42 mount, or Nikon mount (I've been able to confirm that), and ot appears as though it was also available with an FD mount. This is the first version (c. 1967), and the base option was the M42.

With that said, do you think that the Flange to Focal Plane would be long enough to allow for use with an FD>EF adapter? I realize it's only a guess at this point.

Regardless of the lens a glassless FD to EOS adapter will not allow for infinity focus, period. You either deal with that issue or you get one with glass and you deal with the IQ penalty. I'd just avoid FD lenses entirely on EOS bodies (other than the M) unless you're going to do the Ed Mika conversion.

EverydayGetaway wrote in post #16792033
Regardless of the lens a glassless FD to EOS adapter will not allow for infinity focus, period. You either deal with that issue or you get one with glass and you deal with the IQ penalty. I'd just avoid FD lenses entirely on EOS bodies (other than the M) unless you're going to do the Ed Mika conversion.

This is where I have the doubt, and I thinks it's an unusual circumstance. Here's why. If you have a T2 mount lens, which has plenty of room from the flange to focal plane (55mm), and you use a T2 to FD, then an FD to EOS (glassless), there should still be the ability to focus to infinity. The 2 adapters would be thin enough (less then the 11mm threshold) to still get you there.

Yes, it's pointless to try and mount an FD lens to an EF system, that's a given. But this lens was not designed for FD. It was designed to allow the use of multiple bodies by way of an interchangeable mount, and that leads me to believe that he lens has a long flange to focal plane distance. As long as a lens has a flange to focal plane distance greater then the minimum required (44mm in the EF system), it can be adapted to that system.

Basically what I'm saying/asking is, even with the FD adapter that it came with, the actual flange to focal plane distance should be greater then the necessary 44mm (since Nikon has a 46.5mm FtoFP, and Pentax had a 45.5mm). The adapter that is on it should irrelevent to the lens's designed flange to focal plane distance.

Anyone know how to measure a lens's flange to focal plane distance?

KirkS518 wrote in post #16792614
This is where I have the doubt, and I thinks it's an unusual circumstance. Here's why. If you have a T2 mount lens, which has plenty of room from the flange to focal plane (55mm), and you use a T2 to FD, then an FD to EOS (glassless), there should still be the ability to focus to infinity. The 2 adapters would be thin enough (less then the 11mm threshold) to still get you there.

Yes, it's pointless to try and mount an FD lens to an EF system, that's a given. But this lens was not designed for FD. It was designed to allow the use of multiple bodies by way of an interchangeable mount, and that leads me to believe that he lens has a long flange to focal plane distance. As long as a lens has a flange to focal plane distance greater then the minimum required (44mm in the EF system), it can be adapted to that system.

Basically what I'm saying/asking is, even with the FD adapter that it came with, the actual flange to focal plane distance should be greater then the necessary 44mm (since Nikon has a 46.5mm FtoFP, and Pentax had a 45.5mm). The adapter that is on it should irrelevent to the lens's designed flange to focal plane distance.

Anyone know how to measure a lens's flange to focal plane distance?

I don't think measuring the lens will tell you anything, I think the measurement is from the lens mount to the film/sensor plane...

Here is a list of a bunch of lens mounts with their measurements...

http://www.markerink.o​rg/WJM/HTML/mounts.htm

Anything with a distance greater than 44mm can, theoretically, be adapted to EOS, but I don't think you can stack them...

I use OM, M42 and T-2, myself...

You can get T2/T mount to EF adapters on eBay. I have several.

gasrocks wrote in post #16792657
You can get T2/T mount to EF adapters on eBay. I have several.

I honestly think either you aren't reading the posts before responding, or aren't understanding what's going on, or I'm not making myself clear enough. T2 has nothing to do with this lens.

The lens is not a T2 mount lens. It is a lens that can accept numerous mounts through a bayonet system as seen here: http://fotoj.homeip.ne​t …-02/2006_20D_5483-ete.jpg

The bayonet system mount I have (pictured above) has an FD breech mount on the back. That does not necessarily mean that the lens has a flange to focal plane distance of 42mm. It just means that the back end has a Canon FD mount on it, but it could just as well be an M42, Nikon, Oly, Yashica, etc.

If the designed FtoFp distance of the lens is greater then 44mm, I should be able to use a glassless FD>EF adapter and still get infinity focus.

Is that making any sense?

mguffin wrote in post #16792645
Anything with a distance greater than 44mm can, theoretically, be adapted to EOS, but I don't think you can stack them...

I use OM, M42 and T-2, myself...

I think in this case, I would be able to stack them if the lens' design flange to focal plane distance is greater then the 44mm (probably need about 50mm for the 'stacking').

Remember, this lens was not designed like most lenses, which are designed for a specific mount, and would then only have that manufacturer's FtoFP distance. This lens was originally designed to have a longer FtoFP distance to allow for mounting to various bodies. So even though an FD would have a 42mm FtoFP, this lens (I believe) will have a much larger FtoFP, allowing for the stack.

Honestly, if I could just find my FD>EF adapter, I wouldn't have had to ask this.

What I would do is buy another FD to EF adapter. The thinner ones DO allow infinity focus with some long tele lenses. If not infinity, it will be very close or far enough for most uses. (20-30 feet maybe?) Just make sure it is glass-less or has a removable glass element.

Here is a thin one on ebay for $9.95

Macro Canon FD Lens to Canon EOS EF Mount Adapter

http://www.ebay.ca …ash=item23380be​8c3&_uhb=1

msowsun wrote in post #16792850
What I would do is buy another FD to EF adapter. The thinner ones DO allow infinity focus with some long tele lenses. If not infinity, it will be very close or far enough for most uses. (20-30 feet maybe?) Just make sure it is glass-less or has a removable glass element.

Here is a thin one on ebay for $9.95

Macro Canon FD Lens to Canon EOS EF Mount Adapter

http://www.ebay.ca …ash=item23380be​8c3&_uhb=1

That's the one I have that I have misplaced. If I find it, or if I end up just getting another one, I'll report back.

KirkS518 wrote in post #16792775
I honestly think either you aren't reading the posts before responding, or aren't understanding what's going on, or I'm not making myself clear enough. T2 has nothing to do with this lens.

The lens is not a T2 mount lens. It is a lens that can accept numerous mounts through a bayonet system as seen here: http://fotoj.homeip.ne​t …-02/2006_20D_5483-ete.jpg

The bayonet system mount I have (pictured above) has an FD breech mount on the back. That does not necessarily mean that the lens has a flange to focal plane distance of 42mm. It just means that the back end has a Canon FD mount on it, but it could just as well be an M42, Nikon, Oly, Yashica, etc.

If the designed FtoFp distance of the lens is greater then 44mm, I should be able to use a glassless FD>EF adapter and still get infinity focus.

Is that making any sense?

The measurement of the lens doesn't matter once you start throwing on adapters. An FD adapter makes the flange distance set to work on an FD body, thus making the lens effectively an FD mount lens. FD mount lenses don't have the right flange distance to work on an EOS body... I'm not sure what answer you're looking for, but FD mount is FD mount.