I am writing this article solely to address the use of older lenses (aka “legacy glass” on newer, current Nikon and Canon digital bodies. Whenever, people hear about a Nikon vs Canon debate, the first reaction is “oh no, not THIS again”, but there really are some distinct differences between the two systems that should be considered when making an investment into one or the other system. The only difference that I am addressing in this article is the lens mount. Nikon uses the Nikon F mount which is somewhat smaller than the Canon EF mount. – is one better than the other, and if so, why? So let’s review the differences between the Nikon F and Canon EF mounts in detail.
For full disclosure, my interchangable lens cameras have all been Nikons, and except for the Pentax KM I began with in 1976. I have had 2 Nikon film bodies, an F-301 and the F5 I have now, and a multitude of both crop sensor and full frame digital bodies. My main squeeze now is a D810. I have never regretted my decision to stick with Nikon and I managed to dodge the recent issues with Nikon’s quality control. My lenses are all Nikon-made Nikkor lenses which I believe have superb performance and many have been bought previously owned. I love my Nikon gear, but there are some issues with the Nikon F mount when compared to the Canon EF mount. I’ll explain these below.
Nikon F – Mechanical Diaphragm Lever
One of the biggest disadvantages of the Nikon F mount is the mechanical diaphragm / aperture lever that is present on most Nikon lenses. Whether you are looking at a classic manual focus Nikkor, an older “D” or the newer “G” type lenses, all of them require Nikon camera bodies to physically change aperture on every shot if it is set to anything other than maximum aperture. That’s because all such Nikon lenses contain a mechanical lever on the rear side of the lens, which must be engaged to adjust the aperture. When a lens is dismounted, the spring-loaded lever on the lens is pushed back to its standard position, which basically stops the lens down to its minimum aperture. Once you start attaching the lens to a camera body, the corresponding lever inside the camera chamber forces the lens to open up the diaphragm, as illustrated below:
Nikon G Lens Aperture Open
Lenses typically stay wide open at maximum aperture when mounted to cameras, for maximum amount of light to reach the viewfinder and the phase detection autofocus system. Hence, aperture on DSLRs only changes right before the exposure. Once a picture is taken, the lever goes back and the diaphragm mechanism returns to its wide open state to continue providing maximum amount of light to the camera. This means that when shooting with lenses that feature such mechanical levers, the lens must physically stop down and open up every time the camera fires. Since the mechanical lever is physically triggered by the camera, this mechanism must be extremely precise and accurate in order to yield consistently accurate brightness and desired depth of field. However, when shooting continuously in high speed, it is often impossible to yield consistent results, since the mechanical lever might not have enough time to go back and forth quick enough. And if the lever is not precisely calibrated, or potentially wears off / malfunctions overtime, each shot might yield incorrect aperture and brightness.
In contrast, lenses that feature electromagnetic diaphragms do not have any mechanical levers – changes in aperture are communicated electronically by the camera through lens contacts. Such method of aperture control is much more preferred, because lenses can set their apertures consistently and accurately, with no shot-to-shot variation.
Because of the above, using a mechanical lever to change aperture is prone to inconsistency in exposure and potential mechanical issues both in camera and in lenses. Canon realized this and fully moved to electronic aperture control on both EF and EF-S mounts a while ago, and Nikon has only recently started updating its lenses to “E” type lenses with electromagnetic diaphragm mechanism. Unfortunately, such lenses have been limited to mostly super telephoto and higher-end zoom lenses, so despite the obvious disadvantages, Nikon has still been releasing many modern “G” type lenses with mechanical levers.
Nikon F and Canon EF Mount Size Differences
Another key difference is the physical mount size – Nikon F mount’s “throat” diameter is 44mm, whereas the Canon EF mount is larger at 54mm. That 10mm difference might seem small, but it is actually quite important when it comes to lens design. If you have been wondering why Nikon does not release fast f/1.2 primes with autofocus, while Canon has the excellent 50mm f/1.2L and 85mm f/1.2L II lenses in its stable, the answer is primarily in the limitation of the physical diameter of the Nikon F mount. It would be very cost prohibitive for Nikon to try to design f/1.2 lenses with autofocus capabilities, because of space limitations on the rear side of lenses. Such designs would have to be limited to under 60mm focal length range and even then, the CPU contacts would probably have to be put right on the rear element. Anyone who has tried to make the classic Noct-NIKKOR 58mm f/1.2 CPU-capable knows that it requires grinding the rear element to fit the contacts – there is no other way to do it. And forget about longer focal lengths, because it would never fit. In fact, if you look at the rear of the Canon 85mm f/1.2L II, which appears significantly larger than the rear element of any Nikkor, that lens required Canon engineers to put the CPU contacts right on top of the rear glass surface.
In contrast, Canon has an advantage here – shorter focal length f/1.2 lenses in the 50mm+ range can be designed easier, since the mount diameter is large enough to accommodate such optical designs.
Another advantage that some people point out is durability – since the Canon EF mount is physically larger, some people argue that it is also more durable. This claim is easily dismissed because the Nikon F mount is big enough to be quite durable. I proved this while on a safari in Africa when I dropped my camera with a 300mm prime lens attached and did not damage the lens mount. (See post-script)
Nikon F vs Canon EF Mounting Options
Due to the above-mentioned physical differences in lens mounts, along with differences in flange distance, Canon EF lenses cannot be used with adapters on Nikon DSLRs (since the rear element is too large and the flange distance is shorter at 44mm vs 46.5mm on Nikon F), while Nikon lenses can be used with adapters on Canon DSLRs. This is another disadvantage of the Nikon F mount, because it limits Nikon shooters from being able to use Canon glass, while Canon shooters can enjoy Nikon glass on their cameras. In fact, until Canon released its excellent but pricey EF 11-24mm f/4L USM, many Canon shooters loved the results they were getting with the Nikkor 14-24mm f/2.8G coupled with an adapter.
Nikon F vs Canon EF Lens Mounting
When mounting Nikon lenses, you move lenses clockwise when looking from the back of the camera. Canon lenses are always mounted in the opposite, counter-clockwise direction. Not a big deal, but it certainly does take time to get used to this change when changing brands.
Nikon F – Older and Backwards-Compatible
So far I have pointed out the disadvantages of the Nikon F mount, but it does not mean that it does not have its advantages. One of the biggest advantages of Nikon F, is backwards compatibility due to its age – Nikon first designed its F mount back in 1957 and since then, pretty much every F mount lens has been compatible with newly released Nikon cameras. This means that you can grab some really old manual focus classics and still use them natively on modern Nikon DSLRs – something you cannot do with pre-EF Canon lenses. Canon basically ditched its previous mounts in 1987 when the EF mount was launched, without caring for backwards-compatibility. Canon shooters were not pleased, because they found themselves having to get rid of their old lenses and start from scratch with new lenses. Therefore, while Canon provides more lens options for photographers today than Nikon, the total number of lenses one could mount natively on Nikon cameras exceeds that of Canon’s.
Some of the really old Nikon lens designs went through a factory conversion process to allow proper mounting and for metering to work on modern cameras. The designations “AI and AI-s” indicate that the lens is compatible with the aperture index system in the camera body, and if the Nikon body has a “non-CPU” lens set up function in the menu, these old lenses will function beautifully in both aperture and manual shooting modes with accurate readings from the camera’s light meter.
Autofocus compatibility issues with lower-end DSLRs that do not have built-in focus motors have also been addressed for the most part by Nikon, since all modern AF-S lenses will autofocus on any modern Nikon.
Canon EF and EF-S Lens Compatibility
Although both EF and EF-S lenses have the same rear diameter to fit all Canon DSLR cameras, Canon limited EF-S lenses from working on full-frame cameras. This means that if one were to move up from a lower-end APS-C camera to a full-frame camera, they would have to upgrade all EF-S lenses to EF versions first.
Nikon does not have such limitation – DX lenses will work on all full-frame cameras, but if the image circle is not big enough, it will simply have very dark corners in images. One can enable an option in full-frame cameras to automatically reduce image size to 1.5x crop when DX cameras are mounted to avoid darkening of the corners. In some cases, DX lenses at different focal lengths or focusing distances can actually cover the whole image circle of full-frame cameras and those could be used in full-frame mode without issues. This is a great advantage to those who want to move up from Nikon DX to full-frame cameras, since they can first start shooting in crop mode, then upgrade lenses at a later point of time.
My conclusion is that both Nikon and Canon systems offer very strong lens choices. But for me, Nikon is the way to go. I had 2 DX bodies that I used with full frame lenses before acquiring a full frame body. So the “upgrade” was almost painless. I am using a Nikkor 35mm f/1.4 AI-s lens that has superb image quality and it is more than 20 years old. All except the entry level Nikon bodies up to the very newest Nikon bodies D500, D850 and D5 all share the ability to use legacy glass. As Nikon moves into electronic diaphragms for their lenses, these bodies will be able to make use of both old and new technology. I see that as a plus.
I am not starting yet another Nikon vs Canon debate, but rather pointing out the differences between them. And the views expressed are my own.
Post-script: The bayonet mount on the body did however break off. I had to buy a replacement camera body in Botswana and was lucky enough to find a used D7000 for US$250. I had D810 repaired when I returned home. The technician at the repair shop told me that Nikon mounts are designed to break off in order to “save the lens” since lens repairs are more costly. Dropped Canons are more likely to damage the lens mounts which contain electronic contacts.
Thanks to Nasim Mansurov who published an article on this topic in Photography Life on August 10, 2015.