One of the most remarkable changes brought by the advent of mirrorless camera systems (micro 4/3rds, Fujifilm X and to an even larger extent Sony E and FE) is the ability to mount and effectively use almost any old lens designed originally for a 35mm camera system.

With SLR and dSLR camera systems, it was pointless to try and mount lenses designed for another system, and very often, lenses from a previous generation of the same camera system:

• SLRs and dSLRs have optical viewfinders – the photographer needs all the light he/she can get for focusing and composing the picture, and the cameras are therefore designed to work at full aperture with aperture pre-selection – which used to require rods and springs and cams, and since the Canon EOS mount opened the way, now requires electronics. There is no simple way to emulate the pre-selection mechanism of one SLR system  with a lens designed for another one.
• There are also physical limitations:
  • The adapter designed as the interface between a lens of System A and a camera body of System B is more or less a cylinder with the female part of the mount of System A at one end, and the male part of System B at the other end. Such an adapter would necessarily have a depth of 5 to 15mm, which adds to the flange distance. Unfortunately, all digital single lens reflex cameras derived from 35mm SLR systems have a very similar flange distance (from 44mm for the Canon EF mount up to 46.5mm for the Nikon F), and there is not enough room for an adapter (the adapted lens would sit too far from the camera’s film plane, and would not focus to infinite).

Mirrorless camera systems don’t have such limitations:

• They have electronic viewfinders – and offer a clear and bright view of the subject even stopped down at f/16. If fact, most of the mirrorless cameras operate at stopped down aperture even with their native lenses.
• The flange distance of mirrorless systems is much shorter (17 to 20mm for the most common systems), which leaves plenty of room (almost 30mm ) for the adapter if you want to mount a lens designed for a SLR or DSLR system.
• Thanks to their electronic viewfinders, mirrorless systems have multiple ways to assist the operator trying to focus manually (magnifier, zebra, focus peaking).

The use of CAD and CNC is now widespread and it’s easy and cheap to manufacture mechanical mount adapters: users of each of the big mirrorless camera systems have access to adapters for :

• Most pre-AF era mounts for 35mm systems: (39mm and 42mm, Canon FL/FD, Konica, Nikon F, Minolta MD, Olympus OM, Leica M and R, Topcon, …)
• Stranger or more exotic mounts (C mount, Adaptall,  Holga, medium format cameras)

Even if it’s physically possible, mounting recent AF/all electronics lenses is generally pointless – not only you can’t set the aperture for lack of an aperture ring, but you can’t focus the lens because modern lenses are devoid of any mechanical connection between the focusing ring and the focusing mechanism of the lens. Unless a third party vendor develops an adapter which embarks the complex software required to translate the communication protocols of a lens of Brand A into something the body of Brand B will understand.

• As far as I know, it has only been attempted with some level of success between a few lenses with a Canon or Sigma mount and a few Sony bodies (the A7R II or the A6300).

Therefore, the best candidates are lenses from the manual focus era (up to 1985), and the Nikon and Pentax auto-focus lenses designed before Year 2000 – they all still have aperture rings.

Even if it is possible, mounting an old manual focus lens on a mirrorless body is not necessarily the best thing to do:

• in spite of all the focus assistance mechanisms, it’s much slower to get the focus with an adapted vintage lens than with the native auto-focus lens – adapted lenses are not a good fit for mobile subjects, unless you adopt old school focusing techniques (pre-focus, wait for subject to be at right distance, and shoot)
• Older lenses were designed for 35mm film cameras, and are unnecessarily large and heavy when mounted on M4/3^rd and APS-C cameras
• Lots of older lenses were not that good in their heyday, and become really bad if mounted on a camera with a high resolution sensor. It’s true in particular for zooms and to a lesser extent for wide angle lenses.

As a conclusion, why mount old lens on a modern mirrorless body?

• Because you can (of course)

  

• If you already have the lens… Considering adapters sell for $20.00, it’s tempting to buy one to use your old lenses, as a stop gap until you buy a modern equivalent in the mirrorless system, or even permanently
  • All macro lenses are a very good fit because macro photography does not require to focus fast, and old macro lenses are still up to the task, when compared to their modern equivalents
• If you want to experience really exceptional glass
  • Canon FD Aspherical or “L” lenses (50mm f/1.2, 85mm f/1.2) for instance, or some of the gems that Leica, Minolta, Nikon, Pentax and others have produced in the past…
• If the modern equivalent does not exist…
  • a 55mm f/1.2 lens – it doesn’t exist for the Sony E/FE mount
  • a teleobjective with Defocus Control – only Nikon has them
  • a tilt and shift lens (only Canon and Nikon have them)
• or exists but is crazy expensive
  • can an amateur afford the new Sony 85 f/1.4 FE GM?

As a result, old lenses of good reputation hold their value extremely well. Some of the  Canon and Nikon lenses I mentioned above sell for more than $700.00 on eBay.

---

---