It has been almost 60 years since Nikon introduced the Nikon F mount on its first SLR film camera, the “Nikon F“. Since then, Nikon has made over 100 million lenses for this mount without changing any of the physical dimensions, primarily for the purpose of keeping lenses compatible between different cameras, whether film or digital. With its new full-frame mirrorless system, Nikon is now introducing a brand new “Nikon Z” mount, which is quite different when compared to the Nikon F mount. First, it is larger in its diameter, which offers a number of important benefits pointed out below. Second, due to a much shorter flange distance (thanks to lack of the mirror mechanism), it opens up many more opportunities for new types of lenses that we have never seen before.
Let’s take a look at the benefits of the new Nikon Z mount in detail and compare it to other popular mounts, sorted by throat diameter:
|Description||Throat Diameter||Inner Diameter||Flange Distance||Format|
|Leica M||40.0mm||44.0mm||27.8mm||Full Frame|
|Minolta SR||42.0mm||45.0mm||43.5mm||Full Frame|
|Sony E||43.6mm||46.1mm||18.0mm||Full Frame|
|Nikon F||44.0mm||47.0mm||46.5mm||Full Frame|
|Pentax K||44.0mm||48.0mm||45.5mm||Full Frame|
|Leica L||48.8mm||51.0mm||20.0mm||Full Frame|
|Canon EF||50.6mm||54.0mm||44.0mm||Full Frame|
|Canon RF||50.6mm||54.0mm||20.0mm||Full Frame|
|Nikon Z||52.0mm||55.0mm||16.0mm||Full Frame|
|Fujifilm G||62.5mm||65.0mm||26.7mm||Medium Format|
Note (08/31/2018): The above table has been updated with the throat diameter + inner diameter and the information has been corrected for the new Nikon Z mount. It turns out that the actual throat diameter of the Canon EF mount is actually 50.6mm, while the inner diameter is 54mm. This makes Nikon Z mount the largest full-frame mount on the market.
As you can see, the new Nikon Z is larger in diameter than all other current 35mm mounts, whether DSLR or mirrorless. The Fujifilm G is the only medium format system in the above table, provided purely for comparison. While some rumors indicated that the Nikon Z mount is almost as large as the Fujifilm G, just looking at the size of the image sensor itself compared to the mount size shows that the Nikon Z mount is only designed to accommodate full-frame sensors – it will not be able to physically fit a medium format sensor.
Nikon Z Mount Benefits
If we take a look at the size differences between the new Nikon Z mount and the Nikon F mount, we can clearly see the size differences between the two. Nikon increased the throat size from 44mm on the Nikon F to 52mm on the Nikon Z. To visualize this, take a look at the comparison of the new Nikon Z7 camera vs the Nikon D850:
As you can see, while the new Nikon Z7 mirrorless camera is smaller in physical size when compared to the Nikon D850, its mount diameter is visibly larger. Nikon changed quite a few things with the new Z mount. There are now 4 screws to hold the mount instead of 5, and the number of lens contacts has increased from 8 to 11 as well. Interestingly, there are now a total of 4 metal ridges that hold the lens, which means that attached lenses should stay more securely on the Nikon Z compared to Nikon F. This is probably why Nikon also moved the mounting white dot up as well.
So what are the benefits of the new Nikon Z mount? The larger mount opens up more opportunities when compared to the Nikon F. First of all, it provides more space for the sensor to move around when manufacturers add in-body image stabilization (IBIS). Since most mirrorless systems feature IBIS, it is good that Nikon future-proofed its mirrorless mount by making it larger. If there is more space for the sensor to move to, Nikon can implement a very complex IBIS system that not only compensates for camera shake, but also allows to implement such features as pixel shift and star tracking (something Pentax has already done on the K1 / K1 II).
Second, a larger mount gives more flexibility to camera manufacturers when it comes to designing lenses, sometimes allowing simpler lenses to be designed at lower costs. At the same time, mount / throat diameter is not the only variable that impacts lens design – flange distance is also equally important. Shorter flange distance allows lenses to be placed closer to the sensor, which in itself allows lens manufacturers to start building simpler, smaller, lighter and less expensive short focus lenses instead of the retrofocus types. In addition, the throat diameter combined with flange distance determines the maximum possible angle of incidence of the marginal rays from the lens, which is important in designing lenses – generally, the larger the angle of incidence, the easier it is to make high-performance lenses. In the case of Nikon Z mount, that maximum angle of incidence is around 44.09°, which is a lot when compared to the Nikon F that is limited to 12.1°, or the Canon EF that is limited to 18.8°. Even Sony’s mirrorless E mount has a smaller angle of incidence at 31.6°. All this means that the Nikon Z mount, thanks to its large 52mm throat diameter, along with a very short flange distance of 16mm makes it the most versatile lens mount on the market today.
One downside of a larger lens mount throat diameter is lens size and weight issues. The larger the throat diameter, the larger the lens has to be at its mount point, which obviously does impact its overall thickness and weight as well. Also, the shorter flange distance can lead to increased vignetting or discoloration in the corners of an image (although this can be mitigated by making the lens design longer to simulate a longer flange distance). Either way, Nikon made the right choice by going with a large enough mount that is not too taxing on lenses, but also is not so large as to increase the size and weight of each lens by too much. Considering that Nikon is aiming its mirrorless cameras to be compact and lightweight, it would not make sense to go for a much larger lens mount.
Third, considering that the Nikon Z mount has the shortest flange distance, as well as a large 52mm throat diameter, it means that lenses from other DSLR and mirrorless systems could, in theory, be possible to mount on Nikon Z mirrorless cameras. If Nikon mirrorless takes off, we can expect to see third party lens options that will allow mounting lenses from Leica, Pentax and even Sony mirrorless to the Nikon Z mount. Interestingly, other manufacturers will not be able to adapt Nikon Z lenses to their systems!
Lastly, if Nikon ever decides to go with a slightly larger sensor than 35mm, it will be able to do it with the current mount diameter. It will not be able to accommodate a medium format sensor, but perhaps a slightly larger sensor that will provide better low-light performance or increased resolution could be an option.
In short, the Nikon Z mount is clearly superior to the Nikon F in a number of ways.
Nikon F Mount Future
With Nikon moving forward with its first mirrorless system and a brand new mount, should current Nikon DSLR owners be concerned about the future of the Nikon F Mount? I would say “yes and no”. On one hand, Nikon is a small company that cannot allocate unlimited R&D resources towards two full-frame mounts, so we will most likely see more developments taking place on the Nikon Z mount side. This means that the Nikon F is most likely going to see less DSLR cameras and lenses each year, eventually coming to a halt at some point in the future. We have seen this happen with Sony (Sony A mount clearly has no future) and it is likely going to be the case with Nikon as well. On the other hand, while I certainly see Nikon pushing more innovations towards mirrorless in the future, DSLR cameras are going to be around for many years before they are phased out (and even then, there will probably be photographers who will always prefer OVF to EVF and a larger camera to handle). With over 100 million lenses out there, and DSLR camera sales comprising most of Nikon’s sales today, the switch to mirrorless is not going to take place overnight…