Using Micro Four Thirds lenses on Sony NEX cameras

When the first Micro Four Thirds cameras were launched, they became instantly popular for using old, legacy lenses with adapters. Since the register distance is smaller than most other mounts, it is possible to create adapters for mounting lenses from many other systems to Micro Four Thirds cameras. This makes the most sense with lenses that feature a manual, mechanical focus ring and aperture. Even if there exist adapters for mounting Canon EF lenses on Micro Four Thirds, they do not allow for changing the aperture, hence, they are not very useful. This is because the Canon EF mount is an electro-optical system (EOS), which means that there are no manual rings to control the aperture setting.

As the Sony E mount has an even shorter register distance, though, this is one of the few formats that can not be adapted to the Micro Four Thirds system. Sony NEX lenses have a register distance of 18mm, hence, even if a thin adapter was made for using them on M4/3 cameras, you would not be able to focus to infinity with them. This is because the Micro Four Thirds cameras have a register distance of 20mm, too long for the optical formula of the Sony NEX lenses.

But, the other way around is possible: There are adapters for mounting Micro Four Thirds lenses on Sony NEX cameras. As the difference in the register distance is only 2mm, these adapters are very thin. Note that most Micro Four Thirds lenses are electro-optical, just like the Canon EF lenses, so you will not be able to control the focus or aperture from the camera, rendering most M4/3 lenses useless for this purpose.

The most useful M4/3 lenses for adapting on Sony NEX are those that are fully manual, e.g., the Samyang 7.5mm f/3.5 fisheye, the Olympus 15mm f/8 body cap lens, the Cosina Noktor 17.5mm f/0.95, and so on.

Here is what my adapter looks like:



It does not appear to be the best quality, but works ok. You use it as you would expect: The adapter goes on the Sony NEX camera, and then you can mount a Micro Four Thirds lens to it. Note that the adapter has no electrical contacts: Electronic focus operation and aperture operation is impossible, as is the use of the optical image stabilization (OIS), if the lens has this feature.

Using the Wanderlust Pinwide

Here's the Sony NEX-3N with the Micro Four Thirds to Sony NEX adapter, and the Wanderlust Pinwide:



The Wanderlust Pinwide is not a lens, but a pinhole camera body cap. It is recessed into the camera, for a better wide effect. It corresponds to 11mm focal length, hence, behaves like a 22mm lens on a traditional film camera. Which is very wide indeed.

But when used on the 1.5x crop sensor in the Sony NEX-3N, it becomes like a 17mm lens, i.e., extremely wide. See the difference below:

Used on the GH3	Used on the Sony NEX-3N

The problem is the light falloff outside the centre of the image frame. The extra wideness does not help much, as there is a very significant vignetting. The vignetting is caused mostly by the sensor's sensitivity to the angle of the light hitting it: Light coming from a steep angle does not work well, ideally the light should come perpendicular to the sensor. This appears to affect the green channel the most, giving a purple tint outside the image centre.

Using the Samyang 7.5mm f/3.5 fisheye

The Samyang 7.5mm f/3.5 fisheye is a manual focus lens with a manual aperture ring, hence, very well suited for adapting on a non-Micro Four Thirds camera. See the lens mounted below:



One problem with this setup, though, is that the adapter appears to be too thick, placing the lens too far from the sensor surface. This gives problems focusing to infinity. This is still not a fatal problem: You can still stop down the lens to achieve infinity in focus. I had to set around f/8 to get infinity reasonably in focus.

Here are some example images taken on both a Micro Four Thirds camera, and the Sony NEX-3N:

Used on the GH3	Used on the Sony NEX-3N

In the right image, above, you can see that the left and right sides are black. This is due to the built in lens hood: It keeps out light which would fall outside of the Four Thirds sensor surface, hence, giving black sides. Notice also that the black areas are a bit skewed, because the lens adapter mounts the lenses slightly rotated.

In the corners, you can see parts of the image circle ending. The image circle spans 180° field of view, and where this ends, you can see the black bits in the corners. So one advantage of using the fisheye lens on the Sony NEX camera, is that you can crop the image to several different aspect ratios, and still achieve a 180° diagonal field of view. Using a native Four Thirds sensor, you can only achieve this in the 4:3 aspect ratio. Due to the multi aspect sensor, the Panasonic GH1 and GH2 cameras could achieve this also in 3:2 and 16:9 aspect ratios.

Another comparison example:

Used on the GH3	Used on the Sony NEX-3N

Using the Lumix G 14-42mm f/3.5-5.6 kit zoom lens at 14mm

So, the kit zoom lens is of course an electro-optical lens, and you can only adjust the focus and aperture while having the lens mounted to a native Micro Four Thirds camera. However, there is a small trick. You can mount the lens to a Micro Four Thirds camera, turn on the camera, set the focus and aperture you want, take a long exposure, and then remove the lens during the exposure. The lens then has your desired focus and aperture set.

Using this trick, I used the kit zoom lens at 14mm, infinity focus, f/8 aperture:

Used on the GH3	Used on the Sony NEX-3N

Again, we see the vignetting due to the lens hood. This time, though, I could have removed the hood, but I left it on to illustrate that the lens is mounted slightly rotated when using this adapter. We can also see that the image has a bit of barrel-distortion. This is because the lens needs in camera geometric distortion correction to give rectilinear images. And when using the lens this way, there is no such distortion correction done.

Finally, even when pre-focusing at infinity and setting the aperture to f/8, infinity is not really in focus here. Again, this is due to the adapter being slightly too thick, making it impossible to focus on infinity with most lenses.

Conclusion

Using an adapter, it is possible to mount Micro Four Thirds lenses on Sony NEX cameras. However, my adapter was a bit thick, making infinity focus impossible. Also, most electronic lenses cannot be used at all, since there is no way to operate the focus or change the aperture.

This could be a way to reuse your manual focus Micro Four Thirds lenses on Sony NEX, though, like the Cosina Noktor 17.5mm f/0.95, especially if you don't care about infinity focus. That way, you can use the Sony NEX focus peaking as a manual focus assistance.