Since I was throwing this together for Leon, I figured there may be others who will benefit as well.

This description assumes you have a few conversions under your belt and you really prefer/enjoy doing it yourself. I will only address the two major challenges of this conversion for DIYers; the aperture mechanism and the rear element.

There may be better, prettier, and/or more accurate ways to do this, but it works for me and the results speak for themselves, I'd say. Jim, Dimitry, et. al. will probably have a good giggle when they see these photos. I'm OK with that

Before beginning these two sub-projects, it is assumed you have torn down the existing breach-lock mount by removing some small screws in the breach-lock ring and then completely unthreading and removing the silver-coloured breach-lock ring from the barrel. You will have also removed the screws that hold the main assembly which holds the rear element and all the aperture levers & bearings.

Rear Element:

Since the rear element is threaded into the existing FD mount assembly, it makes sense to use at least that part of the assembly in the new mount. Luckily this isn't all that difficult because the main circular raised portion of the the assembly (which holds the rear element) fits quite nicely into a C/Y-EOS adapter. The trick is to remove this central portion (obvious in the photos) from the rest of the "guts" and then install it in the new mount with an adhesive. Also, the internal flanges of the C/Y adapter need to be Dremeled off and the C/Y locking spring needs to be removed. Once the threaded portion is securely installed in the new mount, the rear element can be threaded back into it (take note of the orientation of the rear element before you remove it).

The final product will look something like this (bottom view):

This is great. Thank you for sharing, Paul. I'll give this a try soon... perhaps this might work with alpha mount and no mirror issue (as with a 5D). The rokkor 58 1.2 and 50 1.2 work great with my A900, no mirror issue... that gives me some hope.

ZA mount register distance is 2mm greater than canon so you probably won't be able to get infinity focus.

Thanks, Paul -- this is starting to make more sense to me know......just gotta find the lens
Paul

Thanks Paul for all your hard work putting out these great DIY how-to lens conversion posts. This stuff is great. I might in the future want to do a FD 50 or 55
SSC Aspherical lens conversion, so this helps alot.

Mr. Paul, what will your next conversion be, a FD 135?

wayne seltzer wrote:
ZA mount register distance is 2mm greater than canon so you probably won't be able to get infinity focus.

Minolta/Sony A Mount is 2.5mm longer than Canon FD but only 0.5mm longer than Canon EOS. However the A900 has significantly better mirror clearance than most Canon's, the 58 Rokkor for example requires no mirror modification on either the A900 or Maxxum 9 for infinity focus.

I'm back, and reading your guide word by word now.

mawz wrote:
wayne seltzer wrote:
ZA mount register distance is 2mm greater than canon so you probably won't be able to get infinity focus.

Minolta/Sony A Mount is 2.5mm longer than Canon FD but only 0.5mm longer than Canon EOS. However the A900 has significantly better mirror clearance than most Canon's, the 58 Rokkor for example requires no mirror modification on either the A900 or Maxxum 9 for infinity focus.

Thanks Mawz for correcting my error.
Was also wondering about the diameter of the FD bayonet mount vs. the Sony's smaller than EF bayonnet mounting hole? Is this a problem?

wayne seltzer wrote:

Thanks Mawz for correcting my error.
Was also wondering about the diameter of the FD bayonet mount vs. the Sony's smaller than EF bayonnet mounting hole? Is this a problem?

It certainly could be, depending on how the conversion is done. A mount is second only to EF mount for throat diameter in current mounts, but it's much closer to the older mounts than to EF mount which is why you don't see infinity-capable non-optical adapters other than M42 for A mount.

I suspect you'd be fine for a conversion, but I don't have solid numbers on that.

Leon Noel wrote:
I'm back, and reading your guide word by word now.

Something to look forward to:

Progress

Since I disassembled the lens completely, when I put it back I found a position where the 2 'posts' (from your pictures) are favourable for changing aperture without designing a lot of new parts.

Follows are f16 and f1.2 positions respectively.

Notions:

1 = "whatever was attached on the aperture ring" turned upside down and cut shorter now 'sandwiched' between hence moving the 'posts' along with it for aperture changing.

2 = Stopper (aka stopping the ring at f1.2 to prevent the ring to overturn and get past the assigned range). When it hits the part marked blue on the lens barrel assembly the ring would stop at widest aperture (f1.2).

F16

I am sorry to tell you, it will not work.

The issue is; as you change focus distance, the posts will drop deep inside the barrel and so the aperture will disengage. This is why the post needs to be extended and the fingers need to be recessed as I have done it.

Turn the focus ring and see what happens. With your "clip" in place between the two posts, both posts will need to be extended in order to maintain aperture control throughout the focusing range.

But even that is not enough, because if you leave the clip as is, and extend the posts so they are long enough to keep the aperture working throughout the focusing range, then the posts will be too long and will interfere with the reassembly of the mount.

Hence, the only way is to extend the posts (or one of them, as I have) and then recess the clip or "finger aparatus" as I have done. Both have to be perfectly configured in order to work.

Also, I did not need the piece you marked with blue. My aperture ring stops turning at f1.2 and f16 as it is.

Wow.

I also just noticed that your "clip" is mounted on a completely different part of the aperture ring, about 180 degrees from where I mounted my "finger aparatus". Odd. Maybe that's why I didn't need the "stopper".

Looks good to me, after all, its the end result of taking pictures that's the most important, right?

I rethought the idea of using the original wide rear element holder in a C/Y adapter becasue the fit is so close, but if properly positioned, there is no room for a AF confirm chip. Then, your assembly looks like it is more flush with the EF bayonet ears of the adapter, allowing possible mirror clearance on a stock mirror and clearance for a AF chip? But, the rear element is so far away from the mirror/sensor, the main lens assembly will contact the rear element before the infinity position is reached. So, this begs the question, does the lens focus to infinity?

The general layout looks similiar to the nFD lenses, but the mechanics are a lot different. For example, all versions have an aperture finger to control the iris, but size and shape are all different. I guess the breachlock lenses were more prototypical in the line toward the nFD mount. I had the nFD85L, nFD50L, and nFD50/1.2 all going through conversion at the same time. The backs were identical. The grey cast metal ring that controled the aperture was identical. The black plastic aperture rings were identical and in fact interchangable. They all had weird thread screws. The difference was the aperture fingers. The 85 had one tab, the 50 had 2 tabs. The 85 rear element screwed in from the outside, the 50 rear element screwed in from the inside.

No, mine does not get infinity. I never attempted to get infinity.

What I do get is 14m, which is about 46 feet. My subjects with this lens will invariably be within 46 feet.

However, I suspect that I could get much closer to infinity by simply discarding the internal shroud from the equation (it is sandwiched between the barrel and mount, remember) and then simply turning the rear element in its threads so it does not touch the internal group at infinity.

I haven't felt the need to do so yet, and prefer to keep the internal shroud in place. Also, I enjoy the benefit of a slightly closer min. focus distance.

cogitech wrote:
What I do get is 14m
.
About the same for mine. (FD85L that is). Great writeup, Paul!

Indeed I figured out the 'extended' part of the posts and eventually resorted to your method, ie attaching a ballpoint pen clip on top of 1 post and making a new clamp to wrap around it. The position still stays the same though so it's all good.

I also took some measurements but without the internal shroud (for the sake of infinity) the rear element may touch the next group.

Leon Noel wrote:
Indeed I figured out the 'extended' part of the posts and eventually resorted to your method, ie attaching a ballpoint pen clip on top of 1 post and making a new clamp to wrap around it. The position still stays the same though so it's all good.

I also took some measurements but without the internal shroud (for the sake of infinity) the rear element may touch the next group.



There should be enough thread room there to turn the rear element out slightly more beyond the mount, which should prevent the elements from touching. Of course, this also increases the risk of mirror issues.

Paul,

As always, I am impressed that you take time to share your knowledge, experience and ingenuity with others. This tutorial is yet another example of that generosity.

Hats off to you.

I appreciate you saying so. I wish I knew your name, so I could address you properly, but the best way to thank me would be to convert one of these beauties and then post your shots!