Phase Detect Autofocus with Carl Zeiss Contax G lenses on the Sony a7R II

***UPDATE*** On October 7th,2015 TechArt released v2.1.0 of the firmware described in this post that remedies many if not all of the problems with the initial release. Read on for my original review. I have made edits throughout the text to reflect the new version.

On August 29th, TechArt, maker of the Golden Eagle Contax G to Sony E adapter quietly updated their firmware to support the Sony a7R II. Originally the adapter did not work with the new camera so I contacted the folks over at TechArt hoping against hope that they would soon have a solution. An individual named Lau wrote me back, assuring that an update would be released before the end of August. True to their word, on 8/29 the new firmware v2.0.0, popped up in the TechArt Update app for iOS (download here for iOS and Android). But they didn’t just fix what was broken, they also added support for the 399 fast phase detect sensors on the a7R II!

If you don’t have the adapter, go ahead and skip this paragraph but for owners, it may provide helpful to updating your firmware. Using the app is simple, if not odd:

Here are the Steps:
1. Make sure your phone has Bluetooth activated and launch the TechArt Update app
2. Select the latest v2.x.x firmware from the list of available updates
2. Mount a G lens to the adapter and camera
3. Turn on camera and switch your aperture to f90 (not a typo – use the dial on your camera to set the aperture / not the aperture ring on the lens)
4. Take a picture. It helps if you set the camera to M or S mode, otherwise you are going to have a very long shutter speed.
5. Turn off the camera and remove the lens from the adapter
6. Place the phone right next to the adapter on the camera (yes, the camera should be OFF)
7. Press Update in the Techart App
8. When done with the upgrade, mount a lens, change your aperture to f/2 and start shooting!

The Golden Eagle is compatible with screw drive lenses designed for the Contax G platform. The popular Contax G1 and G2 cameras were rangefinder designs but mated to autofocus lenses produced by Carl Zeiss. At the time of their release, the system was a direct competitor to the Leica M and many professionals considered the Zeiss lenses to be of the same quality.  They were definitely well constructed and as compact as a typical Leica lens of the same focal length and speed.

The original: Contax G2 with Carl Zeiss Planar 45/2 in black

Since the emergence of mirrorless cameras, fans of these lenses have been adapting them to use via manual focus with limited satisfaction. Several years ago, TechArt designed an adapter with a motor to drive the AF screw and developed the electrical and software interface to make everything work – except it didn’t always. The early versions were buggy with frequent lock-ups and slow AF, depending on the cameras’ contrast detection systems. Over the last year, with the latest firmware updates, the Mk III has become dependable (bugs be gone) but some users still complained about the accuracy of focus.

Now, with the advent of the Sony a7R II and its 399 phase detect sensors, the adapter follows in the footsteps of the Metabones EF adapter by supporting fast PDAF. This is truly a revelation as we now have the complete digital equivalent of the legendary Contax G cameras. This combination actually focuses faster than the original Contax cameras did. So now, those looking for the smallest AF lenses of the highest quality on the Sony a7R II have another viable option. Many of us were initially attracted to the system due to its compact size so it is nice to have these beautiful little lenses that give up very little to their larger modern equivalents.

In my stable I currently have the excellent Planar 45/2 and Sonnar 90/2.8 but other good options would be the 28/2.8 and 35/2. The 28mm will have soft corners until stopped way down on the a7R II but there will be no color shift in the corners. I’m going to get my hands on the 35/2 soon so will report back once I put it to work*. Both the 35mm and 45mm lenses are truly tiny but weigh more than newer lenses like the Sony FE 55/1.8. All of that metal and glass in the Zeiss G lenses adds up to a dense little package.

*Update The planar design of the 35/2 was very good but I preferred the look of the sonnar FE 35/2.8 and the fact that the Sony lens focuses much closer. Given that the FE lens will also have access to the more advanced modes of AF (Eye-AF and tracking) and the size is virtually the same, I’m going to stick with the native lens. Still, some might prefer the 35/2 and it worked well on the adapter. I have added some sample photos from outside the camera store to the end of the gallery.

Tale of the tape: Carl Zeiss Batis 85/1.8 for Sony FE vs. Carl Zeiss 90/2.8 for Contax G

Back to the performance of the Golden Eagle adapter on the a7R II – there are issues. I’ve found that when attempting focus at the minimum focus distance (MFD) of each lens, the adapter will hunt badly and worse, slip into a contrast detection mode that will continue to hunt when focused at longer distances. This hunting will quickly worsen until the only recourse is to power down and pop the battery. This problem is exhibited more often on the Planar 45/2 and I couldn’t figure out why. Later I discovered that the more stopped down you are, the less likely the adapter is to slip into this downward spiral. So it makes sense that with the 90/2.8 it would behave better than the 45mm at f/2. The sweet spot for stability appears to be around f/5.6, even at MFD. Hopefully the engineers at TechArt will be addressing the problem and issuing a FW update soon.

*** As of revision 2.1.0, released in October, 2015, the performance is rock solid with AF speed on both my lenses (45/2 and 90/2.8) that rivals a native lens – yes you read that correctly. I’ve noticed some minor hunting in low contrast / low light subjects but nothing major and native FE lenses frequently do the same. AF accuracy is spot on and the MF implementation now works as it used to, meaning that you can engage MF at any time by adjusting the small focus dial on the adapter. This is a major achievement by TecArt and finally makes these lenses viable options that I would feel confident shooting even for paid work.

Take a peek at the AF performance on the 45/2 *** note that this was taken with v2.0.0 of the firmware and does not reflect the improvements in v2.1.0. There is no more “hunt of death”

Gallery of some sample photos from the Planar 45/2 and a7R II below…


  1. I just updated my A7 II and adapter. The combo works really well. It’s fast and accurate.



  2. Chad, thanks for the excellent write-up. Over this past week I got my hands on the TechArt Adapter and ordered some Contax glass to go with the 28mm I’d be using on my Sony a7R II via a MF adapter. I’ll admit my initial reaction was of disappointment; the 28mm hunted like crazy in anything but the best conditions, even with the newest firmware (Ver. 2.2.0).

    Today I received both a 45 and a 90 in the mail – after my struggles with the 28, they’ve been a revelation. They focus fast, focus quickly, they recognize faces with face detect. Add in the size that doesn’t make carrying it a chore (unlike the FE 35), and I think these lenses will spend quite a bit of time on the a7R II.

    The one question I had involves metering. Sometimes, the camera vastly overexposes the image while jacking up the ISO. I’ve set the aperture on the camera to match the lens. But it’s about a step and half to two steps over. I would get it if it were on ISO 100, but it’s putting the auto ISO to 12800 while overexposing. Has anyone else encountered this?



    1. I set the aperture on the camera to 2.0 when using my G45 and then change the aperture on the lens as needed. That has worked fine on my A7 II.



      1. Thanks. Will try this and see how it goes.


    2. Joe has it right – you must leave the camera aperture seeing at f/2, only changing aperture on the lens. Do not match camera and lens aperture settings.



  3. Hi Chad, I spoke to you last year about the TA3 golden eagle adapter. I have one with the original FW that has performed well with the 45 and 90 on my A7. I tried to upgrade the FW to 2.0 last year to work on my A7R2 to no avail. My only conclusion after numerous and varried attempts was that the Bluetooth circuit in the adapter was bad, I could never get the iOS device to see it. I understand that they are now upto 2.2.. I was wondering if you know whether you can buy a new one with that FW preinstalled? I could then leave the original on my A7 and put the new one on my A7R2. I love how these lenses perform on Sony sensors. I can’t find much from them that isn’t about the Techart Pro and I don’t have any Leica lenses. Any help would be greatly appreciated.




    1. I had a similar experience when I follow the provided instructions.. Mine is one of the early release and it came with a bluetooth USB module.. Look at my earlier posting on what I did .. Hope that work out for you.



  4. Are they still making and selling these adapters. The original link doesn’t show the product.



    1. I exchanged emails with TechArt a couple weeks ago. They are planning to release a new version of the G2 lens to Sony mount adapter this summer.



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