or: How I Learned to Stop Pixel Peeping and Love Old Glass
One of the additional rewards of working with a Compact System Camera (CSC) lies in the ability to use other lenses beyond those directly available in your camera’s mount. Many more lenses, actually, as with a little investment and effort you can have access to literally hundreds of optical masterpieces originally designed for SLR and DSLR cameras. In most cases however, only as long as you are willing to forsake some (or most) automated features that come standard with recent models.
No more automatic aperture control (which allows viewing and metering at the lens’s maximum aperture, stops the lens down to the working aperture during exposure, and returns the lens to maximum aperture after exposure). No communication between lens and camera body (to pass on focal length, aperture or distance information). No more autofocus. And certainly no vibration reduction/image stabilization. Although, because every rule requires an exception, some DSLR manufacturers offer an adapter – only for lenses from the same brand – that does preserve several functions when used on their own CSC models.
Less is more
How do we make CSCs compatible with (D)SLR lenses?
The diagram gives the schematic of a DSLR camera in (1), with the essential components of its reflex viewfinder system: a mirror and a pentaprism. The design of the associated lens is matched to the mechanical dimensions of the camera system. Specifically, the lens mount is expected to be positioned exactly at the focal flange distance or register distance d1 from the camera sensor.
As shown in (2), the CSC design gets rid of the large mirror box – it makes them mirrorless. As a result, the lens mount can get closer to the camera sensor: the register distance now has a lower value d2. That makes it possible to develop more compact and lighter camera bodies, as well as smaller and lighter lenses dedicated to this system.
In order to make a (D)SLR lens focus correctly on the CSC sensor, the original register distance d1 must be restored: that is the main task of the lens mount adapter (LMA), which as illustrated in (3) inserts between lens and camera.
Among the current (D)SLR classics, the Nikon F-mount has the longest register distance with 46.5mm, whereas the shortest distance is found at 44mm with Canon’s EF(-S). As for the popular CSC brands, Micro Four Thirds (MFT) has the longest register distance with 19.25mm, then come the Sony NEX E-mount and the Canon EF-M both with 18mm, then the Fuji X-mount with 17.7mm, and finally Nikon 1 with 17mm. The difference between the register distances for (D)SLR lenses and popular CSC models makes it at least mechanically possible to build an adapter for coupling them.
Of course, the image circle projected by the lens at its designated register distance must be large enough to fully cover the CSC sensor. If not, strong vignetting will occur. In most cases, a lens originally designed for use on 35mm film or full-frame or APS-C crop digital reflex cameras will be mounted on a CSC with an APS-C or smaller sensor. The only remaining issue then is the “cropping” of the lens image by the reduced size sensor, reducing the effective angle-of-view of the lens.
The lens adapter: functions and features
Here is what a lens adapter should do, for example to use a Nikon lens on a Fuji X camera:
- Enable the mechanical coupling of a lens and a camera body, using the appropriate mounts at each end of the adapter: a Nikon F body mount at the front, a Fuji X lens mount at the back;
- Restitute exactly the original focal flange distance the lens was designed for, so that a sharp image can be obtained over the full focusing range (including infinity): in this case this means adding 46.5mm -17.7mm = 28.8mm;
- When and if possible, support relevant electrical or mechanical communication between lens and camera body (to assist with aperture control, autofocus, VR/IS, record lens data…): alas no such opportunity in our example;
- When required, provide an alternative way to control the lens aperture setting from the adapter, if the lens itself does not have an aperture ring and the abovementioned communication between lens and camera is not possible: the blue ring on the Novoflex FUX/NIK adapter in the picture provides this for Nikon G-type lenses (including AF-S and DX models);
- Optionally, have a tripod mounting support that comes handy for mounting longer and/or heavier lenses: the Novoflex adapter has this as an option.
In addition, some adapter models come with creative ways to take good advantage of the ‘missing’ register distance that needs to be added:
- Some offer tilt, shift or combined tilt/shift mechanisms, turning the setup into a very portable view camera;
- Some add optical elements into the adapter to reduce the resulting focal length (virtually eliminating the crop factor) as well as boost the light gathering power.
Why use a lens adapter?
Lenses designed specifically for your CSC in most cases will be the preferred option: they are lighter and more compact, usually offer autofocus and sometimes image stabilization, support all camera shooting modes, communicate information data for inclusion with the EXIF data, and are computer designed with the most recent optical formulas and materials. Fujifilm XF-lenses certainly belong to the best you can get, and companies like Zeiss and Samyang offer interesting complements.
So why would you decide to work without the benefits of modern lens technology?
- The lens choices offered within your CSC system may be limited; for a Fuji example: there was no wide-angle wider than 28mm (FF equivalent) until the XF 14mm appeared, no long tele option before the XF 55-200mm, and still no fast portrait lens while we wait for the pre-announced XF 56mm f/1.2;
- If – like me and many others – you have been shooting (D)SLRs for a long time, you may own an assortment of lenses for that system, often manual focus primes: there are great to use with your CSC until an appropriate ‘contemporary’ alternative becomes available, or you simply can save some money if you do not often use that focal length;
- Some of these older lenses may take a special place, because of their specific image rendition characteristics, or just for the memories: it is always a pleasure to ‘revive’ them;
- If you are into close-up or macro photography, you can find and use accessories like extension rings and bellows (these are seldom available with today’s CSC systems);
- Extra features of the lens adapter, such as a tilt and/or shift capability, open new shooting opportunities at a minimal investment;And probably some more that may be relevant to you…
Guilty as charged
While I gradually switched to the Fuji X-system, I thinned my Nikon collection, keeping one full-frame body, three f/2.8 zooms and a lot of primes. The lenses are made by Nikon and by third-party suppliers and span the range from 17mm to 200mm. Some are fairly recent and others are with me since the early 70s. It would truly be a shame to let these lenses sit in the drawer and gather dust. There’s so much photographic delight left with them!
I currently own no less than 9 different adapters for combining Nikon F-mount lenses with Fuji X-mount cameras (no, my second name is not Imelda). They represent the entire range of available adapter types, as far as I am aware. And then one more, for Leica legacy lenses with a 39mm screw thread.
In follow-up blog posts, I plan to offer extensive reviews of all of these. To begin, we will have a thorough look at the top-end models from Metabones, including their amazing Speed Booster. I know that some of you are waiting to hear more about these!