Nikon F vs Canon EF – What’s the Difference?

Although discussing the topic of Nikon vs Canon can lead to unnecessarily long and emotional debates between photographers and I personally find such discussions silly, there are some distinct differences between the two systems that might be worth pointing out for those who consider investing into either system. Some of the differences are related to current technology and it might be a matter of time before either company catches up. For example, Nikon and Sony shooters often brag about the amazing dynamic range their cameras are capable of capturing, pointing out how bad Canon DSLRs look in comparison. And it is currently holds true – Canon has not done well in direct comparisons with other brands on the market, scoring consistently lower in dynamic range performance on each new iteration of its modern DSLRs. However, this is something that Canon could potentially address in the future with newer sensor technologies that provide greater dynamic range performance. On the other hand, other differences might not be possible to address. One such difference is the lens mount – both companies use mounts of different sizes. Which one is better and why? Let’s talk about the differences between the Nikon F and Canon EF mounts in detail.

I have personally been a Nikon shooter for a number of years now and I have never looked back, or regretted my decision to stick with Nikon. Despite some of the recent issues with Nikon’s quality control, I love my Nikon DSLRs and Nikkor lenses for their superb performance and I have been continuously upgrading my gear when significant updates are released. At the same time, there have been times when I was not sure about Nikon as my system of choice, particularly early on when I discovered some of the weaknesses of the Nikon F mount. So what’s the deal? There are several advantages and disadvantages of the Nikon F mount when compared to the Canon EF, so I want to explain these in detail for our readers.

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:

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 addition to the above, lenses with mechanical levers are hard to adapt with other systems via third party adapters. If you have been wondering why adapters for Nikon lenses are hard to use and do not give complete and precise aperture control, now you know why – other manufacturers simply would not have the same lever control mechanism in their camera bodies. An adapter capable of mechanically moving a lever would require a motor with an electronic chip, which would make the solution quite cost-prohibitive.

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. Take a look at the below image comparing the the Canon EF 85mm f/1.2L II with the Nikkor 85mm f/1.4G:

The size differences are obvious. Hence, Nikon would not be able to make such a lens due to the smaller diameter of the Nikon F mount. Shorter focal length f/1.2 lenses would be possible to engineer, but they might require cutting into the glass as described above, which would complicate both the design and the manufacturing process of such a lens, making it very expensive and potentially impractical to sell. Nikon would have to charge thousands of dollars for a 50mm f/1.2 AF-S lens, which would be extremely tough to market. Such a lens would have to be made to order in limited quantities, similar to some of the exotic super telephoto lenses.

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. In fact, the Canon EF mount allows for a 50mm f/1.0 and 200mm f/1.8 lens designs (and we have seen such lenses in the past), which would be close to impossible to achieve on the Nikon F. Having a large diameter lens mount is not just needed for super fast primes though – it can potentially simplify the overall lens design too.

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. I personally dismiss this claim, because the Nikon F mount is big enough to be quite durable and I doubt the Canon EF mount would have a noticeable advantage here…

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 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. This made many Canon shooters unhappy, because they found themselves having to get rid of their old lenses and start from scratch with new lenses, whereas Nikon shooters did not go through the same pains. 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 had to go through conversion to allow proper mounting and for metering to work on some modern cameras, but Nikon offered conversion services for a long time during the transition period. And 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 DSLR. Nikon has essentially moved away from screw-type lenses to lenses with built-in focus motors. But these issues do not have much to do with the actual F mount, which has been Nikon’s standard for many years now.

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, as detailed in Francois Malan’s article. This might be of a great advantage to those who want to move up to full-frame cameras in the Nikon world, since they can first start shooting in crop mode, then upgrade lenses at a later point of time.

Summary

At the end of the day, both Nikon and Canon systems offer very strong lens choices for practically any need. While some Nikon shooters would love to see super fast f/1.2 lenses with AF capabilities, one could argue that such lenses would be hard to use in terms of autofocus accuracy (ask any Canon 50mm f/1.2L shooter) and designing a lens with solid performance at maximum aperture would be extremely difficult and very cost prohibitive. And speaking of cost, I don’t think there would be much demand for a $2K+ 50mm f/1.2 prime when one could get a superb Sigma 50mm f/1.4 Art at a fraction of the cost…

The purpose of this article was not to start another Nikon vs Canon debate, but rather point out the differences between the two mounts. I know that one could argue about each of the pros and cons I pointed out above and I am sure more points could be added by experienced photographers that have used both systems. If you have something to add, please let me know in the comments section below.