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Sony A7R: Lens Support and Lens Mount Torque with Adapted Lenses (Sag, Warp Potential, Shutter Vibration)

For general discussion, see Sony A7R: Adapting Zeiss and Leica Lenses via Lens Adapter.

When adapting a lens to a camera there are imaging goals in mind, such as lens sharpness, speed, bokeh, focal length, etc. With the arrival of the compact 36-megapixel Sony A7R, a limited lens selection along with an EVF and high-res sensor bring new impetus to shoot 'good glass' in a way never before feasible; the D800/D800E still being the only high-res DSLR option, but offering mangled Live View capability, and only on the rear LCD and only useful with a loupe.

But the practical issues of lens adapters might intrude. Consider the three items below: the Sony A7R, the Novoflex Adapter for Nikon Lens to Sony, and the Zeiss Otus 55mm f/1.4 APO-Distagon. The Otus 55/1.4 APO is the finest lens ever made for a DSLR or rangefinder of any brand. And so one naturally gravitates to the idea of shooting it on the A7R.

   
Consider this “lever arm” (physics) and what it would do to a lens mount, temporarily or permanently

While the pictures above are not exactly scale, they are close enough to make the point: a one kilogram lens attached to a lens adapter adding 29mm of extension from the lens mount places a large torque on the mount. The Zeiss 135mm f/2 APO-Sonnar and 35mm f/1.4 Distagon are also large and heavy. Ditto for the Leica R telephotos at 100mm on up.

So the question arises: can the lens mount tolerate this burden? And do you want to take the chance of lens sag and (worst case) actual damage (warping) of the lens mount?

When shooting handheld, one can support the lens with the left hand, but walking around with a large and heavy lens swinging around is asking a lot of the lens mount. It always makes me cringe when I see that.

A DSLR mounts the lens directly, but the A7R has to support the same weight 29mm further from the lens mount (31mm for Canon lenses). The lever arm torque with this arrangement is immediately of concern (sag), but there is a chance that the lens mount might ultimately be bent (warped). I can’t speak to whether actual damage will happen*, but it’s a lot to ask of a lens mount, and I don’t want built-in tilt when I shoot (lens sag).

This issue is already there with large lenses mounted directly to a DSLR; I would never willingly tripod-mount my camera with a 70-200mm f/2.8 lens attached (though an f/4 is generally fine). Leica acknowledges the torque issue by detailing (in the manual) specific weights that are tolerable using the Leica R-adapter M: over those weights the camera + lens ought to be mounted using the tripod collar.

* I once damaged the lens mount on my Nikon DSLR and it cost $550 to replace the mount. The damage (warping) is/was invisible to the eye, but caused asymmetric blur in ever image I made.

Mitigation via tripod collar on lens adapter

The Novoflex ASTAT-NEX Tripod Collar can be used with the Novoflex Adapter for Nikon Lens to. The collar attaches to the lens adapter, and that is what is tripod-mounted. This eliminates the stress on the lens mount by asking the adapter to support the camera on one side and the lens on the other; the lens mount no longer directly support the weight of the lens. This see-saw support is far from ideal from a stability standpoint.

Now consider the fact that shutter vibration is a problem with the 24-megapixel Leica M Typ 240 using the Leica R-adapter M with 90+ mm lenses. The M240 has no electronic first curtain*, and apparently neither does the Sony A7R*. And yet the A7R is 36 megapixels and the Novoflex adapter is thicker and less solidly built. Guess what the real quality concerns are with adapting high performance lenses?! Blur from camera movement (vibration).

* In my view, Sony’s decision to include a 1/8000 second shutter speed is an ill-considered compromise versus a low vibration shutter offering only 1/4000 speed.

** An electronic first curtain allows true vibration-free exposure ad with the Canon “Mode II” exposure option. Many cameras operating in Live View instead slam the shutter closed, then reopen the shutter (often without a delay). The dual shocks degrade image sharpness, particularly on a see-saw rig as described above.

Roy P writes:

Do you have your A7R yet?! I saw your commentary on the 75 APO Summicron-M vis-à-vis the Zeiss Otus 55/1.4 and the Sigma DP3, and looked over your DeChambeau Yellow Trailer (Leica 75/2 APO on M240) images. I can tell you it was quite depressing for me as an owner of the Leica 75 APO ‘cron. I am really eager to see how the 75 APO fares on the A7R.

I really want to buy the Otus 55/1.4, and the Otus 85/1.4 when Zeiss comes out with it. The only problem, I don’t know if I should buy the ZF.2 or wait for a Sony A or E mount version of the lens. It’s a real head scratcher that this lens is available for the two cameras that provide zero support for manual focusing, and not for the cameras that provide superb support for MF (Sony A99 and A7R). Do you have any insights on whether Zeiss plans to offer this lens in an A or E mount or both?!

BTW, I just got back from a trip to Asia, and had a chance to look at the new Sony RX10 at the Hong Kong airport. What a great little package! Superb handling, a lovely looking Zeiss 24-200mm equivalent lens at a constant f/2.8. Since you liked the RX-100, I thought I’d mention this camera. I damn near bought it, but I just can’t bring myself to buying any camera that has a sensor even smaller than a Micro 4/3. If Sony puts out even an APS-C version of this, I’d probably jump on it.

DIGLLOYD: I expect my A7R very soon.

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