A Nikon F mount lens is small enough to fit (via an adapter) into a Canon EF mount camera.

Is this by design (IE did Nikon design the whole bayonet to be small enough, or Canon design the EF to be big enough) or just pure luck?

  • You are asking for an opinion, I'd say. Who can really tell if a big company like Nikon does something like that on purpose or by coincidence? – Esa Paulasto Jul 26 '15 at 10:09
  • Well not really, It may be well known!! (but not to me) – Digital Lightcraft Jul 26 '15 at 10:14
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    I think the one thing we can say with confidence is that Nikon did not design the F mount to be compatible with the EF mount. Why? Because EF is ~20 years newer than F! – Philip Kendall Jul 26 '15 at 10:38
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    Well thats a start! so could it be that he EF was designed to be BIG enough to fit an F lens? – Digital Lightcraft Jul 26 '15 at 10:39
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    Only the original Canon EF designers can really answer this question, but I say that this 'compatibility' has more to do with Canon's choice of slightly shorter nominal flange focal distance than anything else. It's not until recent times that many people started obsessing about jamming old glass on mismatched bodies, so insinuating that Canon designers in the 1980s conspired to 'steal' future Nikon users by making their lenses (vaguely) useful on Canon EF and other bodies is nonsense. – HamishKL Jul 26 '15 at 21:08

If you read Canon's public statements at the time the EOS system/EF mount was introduced in the late 1980's, they spoke of the longer 44mm registration distance and larger diameter flange of the EF mount, when compared to their existing FD mount that had a registration distance of 42mm, as leaving room for future capabilities. If they had been concerned with allowing non-EF lenses to be easily adapted to their new mount, they would likely have made the registration distance shorter than 42mm so that their current customers' own FD lenses could be adapted to the new system. Their primary emphasis, though, was on the all electronic communication between the camera and lens at a time when others, including Nikon, were attempting to enter the age of digital control systems using existing mechanical connections between body and lens. Canon boldly stated that it was time to make a total break from the past and create a new mount as modern as possible without regard to the usability of the pieces of previous systems.

Most early auto focus lenses by other manufacturers put the motor in the body and created an additional mechanical linkage to move the focus elements in the lens. Canon took a big risk and created a totally new system that they have been reaping the benefits of for nearly two decades in terms of superior performance when it comes to auto focus speed, accuracy, and tracking of moving subjects as well as the capability of all EF lenses to be fully functional with all EOS cameras.

The risk was that the new system totally abandoned the system their customers were currently using, so there was nothing other than the performance of the new system to keep their customers from jumping ship when the time came to replace their FD mount cameras and lenses. In that scenario, the last thing Canon wanted was for Nikon lenses to be perceived as superior to the new Canon lenses - with no customer base already entrenched around the new EF mount their customers would have simply moved from the Canon FD system to the Nikon F system (and some did just that for a variety of reasons) instead of to the Canon EOS/EF system! But the advantages of the all electronic connection and the improved performance for things such as action and sports photography also attracted a lot of Nikon users to the Canon fold.

I doubt very seriously that leaving room to adapt Nikon F mount lenses was much of a consideration. After all, the capability to do so was also there with the 42mm FD and FL mounts that Canon used from 1964 until 1990, yet actually mounting Nikon glass on Canon bodies was a very small niche sector of the photographic landscape at the time.

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  • Good answer :-) - so we are going with "its almost definitely just coincidence" – Digital Lightcraft Jul 27 '15 at 8:10
  • I think you can remove the almost. Everything that went into Canon's decision to scrap their own FD/FL mounts and design the EF mount from scratch based on what they thought the future, not the past, would require confirms this. By going from 42mm to 44mm they actually provided Nikon with an opportunity, should they have decided to introduce a totally new mount, of going shorter than 44mm and making it easy for Nikon owners to use Canon glass. Looking back we now know that Nikon hung on to the F mount, but no one knew if they would or not back then. – Michael C Jul 28 '15 at 1:15
  • Look at it this way: the various mounts have always been pretty much proprietary for a reason - to force the owners of a particular camera to also buy their lenses from that same manufacturer. Until the very recent past, third party lenses were for the most part either vastly inferior to top tier OEM lenses from Canon, Nikon, Minolta, Pentax, etc. (Tamron, Sigma, et. al.) or vastly more expensive (Zeiss, etc). Neither Nikon nor Canon wished to make it possible for the owners of their cameras to use lenses from their arch-rival! – Michael C Jul 28 '15 at 1:26

It's almost certainly a co-incidence. Adaptability of foreign lenses wasn't a big thing back then in the SLR world (it was more common with medium format cameras). The simple reason for this was that camera bodies were much cheaper as they were essentially just light tight boxes with a shutter, mirror and viewfinder (you might get electronic metering or an electronic shutter).

Whilst you might have to spend $2000 on a full frame body now, you could get a full frame camera body for considerably less. So if you really wanted to use Nikon lenses, you wouldn't mess around with adapters, you'd just buy an F-mount camera (it didn't even need to be a Nikon, other manufacturers offered F-mount SLRs).

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    Excellent point about the relative prices of camera bodies back in the film era. Unless you were a working photographer that needed a very robust body to take the abuse of constant use, you sunk all of that money we now spend on digital bodies into film and developing. – Michael C Jul 28 '15 at 1:24

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