Lens Mounts: Sony FE

Pekka Buttler, February 2023

Sony FE/E/NEX mount naming:

First, there is some confusion regarding the name of the mount, partially due to the evolution of the mount, but mostly due to haphazard use of terminology in online forums. Technically, the Sony FE mount comprises of:
• The Sony FE mount (full-frame), and
• The Sony E mount (APS-C).
Regarding the physical and electronic properties of the mounts, both are identical, and the difference between Sony E and Sony FE (when used correctly) mostly indicate whether we’re talking about a lens/camera intended for full-frame or APS-C crop.

The issue is further complicated by that the first cameras introduced for the Sony E mount (2010–2013) were all called “Sony ⍺ NEX (something or other)”, and the name “NEX” has stuck as being synonymous to Sony E/FE. This article will however be systematic in calling it the Sony FE mount and using the “Sony E” name only to denote APS-C crop bodies.

Sony FE basic history and development

After Konica Minolta decided to stop producing cameras, Sony acquired that camera business (including designs and patents) in 2006. While Konica Minolta had been somewhat lacklustre in its attempt to compete with Canon, Nikon and ilk in the dSLR market, Sony approached the task with somewhat more vigour (and immensely greater resources). As a result, Sony introduced 16 new dSLR models before 2010 (including two full-frame dSLRs) and quickly reached approximate parity with Canon and Nikon.

In 2010 Sony went on to make three breaks with the established logic of the market.
• Firstly, Sony introduced the SLT (single lens translucent) concept – an SLR-like camera, but without a swinging mirror. Instead, SLT cameras use a fixed, semi-translucent mirror, phase detect-AF and electronic viewfinders. In essence, the SLT combines some SLR-like features (such as sensor-independent phase detect) and backwards compatibility with existing Sony/Minolta SLR/dSLR lenses, with mirrorless features (electronic viewfinders and on-display live view).
• Second, Sony introduced the ⍺ NEX line of APS-C sensor compact cameras using the new Sony E mount. The ⍺ NEX line of cameras were not the first pure mirrorless cameras (both Panasonic and Olympus had preceded the NEX), but they were the first mirrorless cameras with an APS-C size sensor, and clearly showed what the technology is capable of.
• Third, pre-empting the major competition by more than a decade, Sony announced that it would no longer develop digital SLR cameras.

During 2010–2013 the Sony E/NEX lineup of cameras and lenses continued growing. From the beginning it was obvious that the Sony E mount was dimensioned in order to allow for a larger than APS-C sensor, and the public was eagerly expecting Sony to take the E-mount full-frame…

One audience that had been especially enamoured by the NEX/E-mount were all those who realised that the NEX cameras offered the (to that date) best avenue of giving legacy lenses a new lease on life.

In 2013 Sony unveiled the ⍺7 and ⍺7R (followed in 2014 by the ⍺7S) – a trio of differently targeted full-frame mirrorless cameras. Not only were these the first full-frame mirrorless cameras1, they beat the competition to the punch by a wide margin. Leica introduced its first full-frame mirrorless only in October 2015, followed by Nikon (Z6 & Z7) in August 2018, Canon (EOS R) in October of 2018, Panasonic (S1) in February 2019 and Sigma (Sigma fp) in July 2019.

More importantly, all those lens hackers who had found ways to use their legacy lenses on the Sony E system were gladdened to find that they could take their lenses and their existing adapters and just plug them onto Sony’s new full-frame marvels and get the same field-of-view that the lenses were originally designed to produce.

Sony FE mount specifications

Mount type: Bayonet mount (lens release on camera)
Flange focal distance: 18,00 mm
Sensor size:
• Sony FE: 36,0 mm x 24,0mm (‘Full frame’)
• Sony E: 23,4 mm × 15,0 mm (APS-C)
Mount communication:
• electronic only (aperture, autofocus, focusing distance)
• 10 electronic contacts (spring-loaded at the camera’s end)

Adapting Sony FE lenses

Sony FE has one of the shortest flange focal distances in the industry, so Sony FE lenses are not easy to adapt to other systems. In fact, there is only one comparable size sensor system that can adapt Sony FE lenses: Nikon Z. Not only is the Nikon Z mount’s flange focal distance sufficiently much shorter to allow adapting Sony FE lenses using a dumb adapter ring (see here), there even is a Sony FE->Nikon Z smart adapter (See here. Caveat: I have not tested it)

Adapting to Sony FE cameras

Obviously, the Sony FE system was never intended purely as a platform for using legacy lenses. Instead, Sony showed the level of magic a full-frame mirrorless system can achieve (but considering JAPB’s focus, we won’t go further into that). Suffice it to say, that for several years post introduction, the Sony FE system was the undoubtedly best system to breathe new life into legacy lenses. Even today, the first-mover advantage still makes itself known in that there is not another mirrorless system that would offer as wide a range of various adapters.

What I find especially noteworthy is that Sony went out of its way to offer Sony FE system adopters a wide range of in-house adapters that allow people with a heavy investment in the Sony A/Minolta A system to keep using their lenses on Sony FE cameras. In this respect, Sony’s commitment to backwards compatibility is broader than that of Canon (who also offer adapters but with fewer functionalities) or Nikon (who also offer an adapter, but allow only the most recent lenses full functionality).

So, what can you adapt to Sony FE cameras? Almost anything.

Obviously you’ll need some form of adapter (but even a conservative person as myself has freelensed with the Sony ⍺ 7 (when lacking an adapter)).

Secondly, you’ll need a lens that has a native flange focal distance greater than 18,00 millimetres, but with the exception of some 8 mm and 16 mm (motion picture) film camera mounts (C-mount, CS-mount, D-Mount), many industrial&X-ray mounts and some other mirrorless mounts, that hurdle is not difficult to surmount.

Third, unless you want to manually have to crop every shot in post, you’ll need a lens that produces an image circle that reaches the APS-C sensor area. Beyond those already excluded by the flange focal distance requirement, only the Pentax-110 system, the Olympus Pen-F system and a number of video camera systems can pose issues (even then some lenses will have a sufficient image circle).

Finally, there are some modern lenses that pose limitations because those lenses are too dependent on electronics. This obviously applies to any lens where the aperture mechanism is electronically controlled, or that do not offer any affordance for manual focusing. In order to be able to use such a lens, you will need a compatible smart adapter that will facilitate two-way electronic communication between the body and adapted lens. On the other hand, should you have such an adapter (and should it support the lens in question), it works as a native lens would.

Police coming to investigate reports of something fishy going on.
Canon EF-S 18-55 kit lens, no-name smart adapter and Sony ⍺7R2.
Camera automatically selects APS-C crop mode and everything (including face detection) works.


1 Technically one could argue that Leica was first with the introduction of the full-frame M9 in 2009, but due to several factors (especially the rangefinder approach) I think it does not exactly compete in the same pool.

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