Convert Canon breech mount to newer bayonet

Discussion in 'Canon FD' started by NLsafari, Jan 3, 2021.

  1. I have a Canon FD lens with the old breech bayonet mount and I am thinking of changing it to the the NEWER bayonet style mount. Is this something that is a "BOLT ON" or is it a complicated conversion?
    Alex_Es likes this.
  2. cmuseum

    cmuseum cmuseum

    It's not just the mount that is different but the entire construction. With the New FD bayonet style mount almost the entire lens is rotated. Only the inner rear-most part of the mount remains in a static position. Breech-lock lenses are quite the opposite: The entire lens remains in a static position, except for the breech-lock ring.

    It is neither bolt-on nor a “conversion” which can be done with reasonable effort.
    Alex_Es and NLsafari like this.
  3. There is no real difference. All FD lenses fit and lock onto FD bodies. Canon only "improved" the LOCKING mechanism for FD lens mounts. It changed nothing for the FD system. The mount is still the same.
    Alex_Es likes this.
  4. Cmuseum is right, totally different engineering was used in producing the FDn series of lenses. It's not just a matter of interchanging lens mounts. There's much more to it than that.
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  5. If you can adapt the Canon breech bayonet to a NIKON bayonet mount ... and I have seen lenses on ebay offered like that, it should be theoretically possible to do a conversion to a Canon bayonet mount.
  6. Why you'd want to do that is beyond me. IMHO the breach lock is vastly superior
  7. Don't worry about changing the mount since there is no real need. I used lenses of both for years, Many actually say the breech is stronger and from memory I have to agree. The bayonet is likely faster and easier to use, hence I believe most if not all lens mounts are like this now.
    Alex_Es likes this.
  8. You can't adapt a Canon R/FL/FD to a Nikon mount and have it focus to infinity, without installing some sort of image-degrading optical element. The flange-back distance for the Nikon F mount is 46mm. The flange-back distance for the Canon is 42mm. However, you can mount a Nikon F lens on a Canon R/FL/FD body with an adaptor. Canon made such an adaptor back in the 1960's. A rare, collector's item today.
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  9. You may ask why would a sane person want to make such a conversion? My youngest doesn't know his own strength and is lacking some dexterity. During the holidays he was changing a lens on his Canon-F1n and in the process of putting the rear cap back on did not notice it was not properly aligned and tightened so hard its impossible to loosen. I drilled two 1/8 in. holes in the rear cap, close to the back so as not to damage the rear element, and passed a thin steel rod through them to increase the mechanical advantage when I applied force but I still could not loosen the rear cap. It will require an expert to get it off. So I was thinking why not convert his FD breech bayonet lenses to bayonet and prevent this from happening again. Its probably easier to get him bayonet lenses in the first place.
    Last edited: Jan 4, 2021
  10. Oh, I dunno. After you've done it once you tend to be more careful thereafter. BTDT
  11. I'm confused. Although I don't have any FL-mount lenses it was always my understanding that they could be mounted on FD mount
    Canon FL lens mount - Wikipedia where it says -- "FL lenses can also be used on FD-mount cameras.". (stopped down)

    I don't think there is any practical or cost-effective way to make the FL lenses other than stop-down, no matter what camera....
    Alex_Es likes this.
  12. You went just one step too far back, JDMvW ;).

    NLsafari isn't talking about the FL breech lock series of the 60s but the followup original FD series of the 70s (which were basically the FL mount updated with open aperture metering coupler and AE setting). These original FDs suited most traditional Canon customers just fine, until Canon set off the hydrogen bomb of the bargain AE-1. Suddenly, a million Instamatic-addled Average Joes/Janes that would never have been caught dead with an SLR before went rushing into Canon's arms. Surprise, surprise when 3 out of 4 could not figure out Canon's fussy breech lock mount, resulting in their lenses dropping off the camera to the floor in droves.

    So, Canon inverted the breech mechanism into a faux bayonet mount, to create "lenses for consumers not photographers". This was such a complex re-engineering project that there was no point in doing it unless the tooling would be consistent over the entire lens lineup: within a few years as stocks depleted of FD breech lenses they were all replaced by FDn fake-bayonet.

    Evidently NLsafari feels his son is having trouble with the older breech mount and may be better off with FDn instead. But there is absolutely no way to convert FD breech to FDn bayonet: as others above have noted it isn't just mount but the entire lens barrel that was reconfigured. The optical formulas often carried over, but the entire barrel and mount were new. Those who prefer the bayonet action would need to sell or trade their breech FDs and replace them with FDn versions. Since many silver breech ring lenses have some collector value now, the trade costs should be fairly reasonable (except on exotic pro lenses).
    Last edited: Jan 11, 2021
    ] likes this.
  13. As the OP gives his reason for wanting to switch mounts, he should also note that the newer mount is not problem free as many here have had the problem of a stuck release button.
  14. Much as I like the Canon FD system, I can't help thinking that the lens mount had all the attributes of being "designed by a committee". No wonder they abandoned it in favour of the EOS mount - to the disgust of users with a nice set of FD lenses.
    Alex_Es likes this.
  15. Tony Parsons

    Tony Parsons Norfolk and Good

    If it's only the cap that is stuck, why not sacrifice it (a Dremel should do it) and purchase a new cap ?
    Alex_Es likes this.
  16. I sure did, I never had any breechlock FD, and I'm getting fuzzier all the time anyway...:rolleyes:
    Alex_Es likes this.
  17. awahlster

    awahlster Moderator

    OH I have a different opinion the original FD mount with the rotating ring is AWESOME you place the lens against the body and the ring moves itself just enough to keep the lens from falling off. Granted you still need to turn it to full lock but thats fine. Now on a Nikon or other bayonet lock you needed to find the button to relase the lens while on a FD lens all you needed to do was turn the ring your fingers could be on the ring any where. No I think the Original FD mount was genius. The later nFD mount was done to make the Canon mount more like other companies and to save weight and production costs. As to why they dropped the nFD mount when they went to AF thats simple there just plain wasn't enough acreage for all the electrical connection on the nFD mount. Also they needed to gain some focal distance from the film plane.
  18. Maybe it's a 'Marmite' thing as we say in the UK. Maybe it's just what you first used.

    I have had FD stuff for 30 years (a T90 bought in late 1990) and have always avoided B/L lenses wherever possible. I find them fiddly to mount and remove compared with FDn. On the newer lenses the lock button is consistently positioned so if you have a finger on that the alignment is pure muscle memory. A B/L lens can be any way up so you need to look at what you are doing. Plus, on my one remaining B/L lens, the partial turn has failed - OK with had it been a 50/1.8 but not so much for a beast like the 55/1.2!

    It's closer on removal, but I still prefer the newer lenses. With a FDn lens to push the button you get a good grip on the lens and twist, whereas with the B/L sometimes feels like you need three hands - one for the camera, one for the lens and a third to turn the ring...
  19. Each version has its advantages.

    Influential magazines of the day widely considered Canon's breech lock the most technically sophisticated 35mm mount of the era, because it combined the speed of bayonet mount with the custom-each-time snugger fitting of M42 screw mount.

    But like many "perfectly engineered" creations, it faltered somewhat at the human interface level. While Canon did cleverly integrate a self-starting breech, this did not overcome the fiddly aspects of mounting the lens with no tactile (and limited visual) feedback, so more often than not a lens would fail to engage self-start and simply fall out of the mount. While a minor occasional nuisance to enthusiasts and pros, this was a total PITA for the utterly inept amateurs who began flocking to SLRs in the mid 70s (lured by the heavily-misrepresented marketing of AE and winders and sports celebrities).

    After Nikon finally rid itself of its cumbersome pin-and-prong lens coupling in 1977 with AI, and Pentax' earlier heavy promotion of its transition to bayonet from M42, Canon no longer had any competitive cover for the quirks of its own breech lock system. Combined with the exploding sales of its consumer-oriented AE-1 camera, Canon was left with no choice but re-engineer the breech ring into a goof-proof quasi-bayonet system. In this they succeeded remarkably well, but a lot of Canon fans still prefer the breech system operation. Also the lower-end non-pro breech lenses were of classic-era uncompromising build quality, while the many of the FDn revisions became increasingly plastic.

    Other than Canon in 35mm format, two medium format systems, Mamiya Press rangefinder and Kowa 6 SLR, employed breech lock mounts. These were much larger and slightly cruder than Canon's (no spring loaded self-start, breech ring on the body instead of each lens). The Press is a bit fiddly but fairly simple once you get the hang of it. The Kowa needlessly saddles you with an infuriatingly balky fingernail-shredding breech ring release lever, which defeats the whole purpose of having a breech mount.
    Last edited: Jan 19, 2021

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