Much more fun than expected – the Contax G 90/2.8 on the A7 II

Once in a while you are hit by some GAS – Gear Acquistion Syndrome – end up buying a new camera or lens, and only some weeks later you realise there is a really cool side benefit to your newest purchase that you were not aware of before.

In my case, I swapped my beloved Sony A7R for an A7 II – less resolution, yes; but with 24 MP still in the same league that all the highly praised newest Leica cameras are in, and so I thought, if famous Leica photographers can live with that, so should I :) Wanting to do less tripod photography and realising that autumn and winter are now coming up – I thought an A7 II with built-in stabilisation is just the right thing to have right now.

Zeiss Contax G 90/2.8 on A7 II
Zeiss Contax G 90/2.8 on A7 II

A forgotten gem in my lens collection

After some weeks I did remember my old Techart Contax G adapter – after the last firmware it would not work at all with the A7R again due to that camera lacking a phase detection AF feature. (Prior to the firmware update, it would kind of work, but way to unpredictable for any real photography.) I found it sad that the adaptor even did not allow working with manual focus on the A7R, but that’s the way Techart did it. Anyway, I threw the adapter on the A7 II, added my – so far only – Contax G mount lens, the Zeiss 90/2.8, and went to the streets.

Zeiss Contax G 90/2.8 on A7 II
Zeiss Contax G 90/2.8 on A7 II


It works a treat, I have to say! All the shots shown in this blog post are taken with the 90/2.8 in Cologne, the Westerwald (a nice spot if you like the German countryside) and Tilburg (IMO one of the coolest cities in the Netherlands, go visit it if you like all kinds of festivals and interesting activities!).

A note: All the pictures are taken in RAW and processed (colors, vibrancy, shadows, exposure) just to my personal liking, as I always do. However I did not add color correction (CA’s etc.) or removed vignetting. In that respect, what you see here is what you really get with the Contax G 90/2.8!

Rheinauhafen No. 14 (Sony A7 II with 90/2.8 at f/2.8)
Rheinauhafen No. 14, Cologne. (Sony A7 II with 90/2.8 at f/2.8)

This is perfectly useable for everyday use, and I would not hesitate to take this lens + adapter combo anytime with me for a trip for serious photography. But still there are some culprits you should be aware of. While really working well, the Contax G lens with Techart adapter does not work as perfectly as a native Sony FE-mount lens would work. How can it, given that the lens was made for an extinct analogue camera system some 20 years ago.

First, I think the AF is really fast. But I am the opposite of a sports photographer. :) So better don’t listen to me probably :) Let’s say for the shots in this blog entry, the AF was always super snappy and fast enough. It uses the A7 II’s phase detection system so you can’t move the AF point all the way out to the frames edges as you can when using a native FE-mount lens. But at the same time, using phase detection means that the lens normally does not “hunt” or move back-forward. It just moves in the correct direction to lock focus, like you would expect any standard DSLR lens to do. In this respect, the focusing experience is not “mirrorless like” any more. Kudos!

Sandy beach at Cologne Rodenkirchen. (Sony A7 II with 90/2.8 at f/2.8)
Sandy beach at Cologne Rodenkirchen. (Sony A7 II with 90/2.8 at f/2.8)
Cologne features the oldest motorway bridge in existence. Really! (90/2.8 at f/2.8)
Cologne features the oldest motorway bridge in existence. Really! (90/2.8 at f/2.8)

The two culprits – First: autofocus accuracy at very wide distances

A drawback of the phase detection system and probably the old-fashioned screw-drive AF system of the Contax G lenses is that focussing accuracy is not 100% like it is with modern mirrorless lenses. Especially on very far away subjects – such as the bridge in the picture above – it might be off at times. (In case of the picture above, it was spot-on, though.) You won’t see these slight focus errors in the viewfinder unless you zoom in – so if you are worrying, you should fine-tune the focus manually before you take the shot.

The way this works differs from other Sony lenses as the Techart uses its own firmware. For a start, you can’t directly select Manual Focus or DMF modes in the camera once any Techart adapter is mounted. You do have to use AF-S or AF-C. So after you half-press the shutter, the camera focusses automatically. But when you let off the shutter button after that, you are now free to manually focus (using the small wheel on the adapter) and you are also now free to use the camera’s zooming-in feature to really judge focussing. Once you are finished, then simply press the shutter button again, and it takes the picture.

So why is there a dedicated focus wheel on the adapter? The Contax G lenses never had focusing rings. The whole camera system was designed with AF-only use in mind. But Kyocera (the makers of the Contax G system) knew that AF will sometimes fail so they had to design something that allowed for manual focusing. That’s why the Contax G1 and G2 cameras have a focus wheel built in the body. The lenses can only be focused via the screw-drive mechanism that is built into the bayonet mount. So if you turn the focus wheel, it tells the AF motor (in the G1 or G2 camera, also an AF motor is built into the Techart adapter) to turn the screw-drive mechanism and thus change the lens’ focus setting. It sounds a bit awkward but I have to say it works very well. Switch to the magnified view, turn the small wheel on the adapter and you’ll see how the focus really snaps.

Elko the boat. Tilburg, Piushaven. (90/2.8 at f/8)
Elko the boat. Tilburg, Piushaven. (90/2.8 at f/8)
Cologne University Boat. (90/2.8 at f/2.8)
Cologne University Boat. (90/2.8 at f/2.8)

Second culprit – you should always use AF at open aperture only

The second drawback is that focussing is only accurate at open aperture (naturally). Everyone knows exept Sony. All their gorgeous mirrorless cameras focus stopped-down. So this problem applies not only to the Contax G lenses, but in fact to all Sony FE lenses as well. (My shots with the FE 50/1.8 at f/8 come out really very often misfocussed. At f/1.8 it’s always perfect.) So what do you do? (1.) open the lens aperture to f/2.8, (2.) autofocus by half pressing shutter button, (3.) close aperture to whatever you’d like, (4.) take shot and you are done.

If you, say, take a shot at f/5.6, and follow the steps above, you also don’t need to worry about any small autofocus errors any more. So far, I did never encounter an autofocus error that was so big that it would have ruined focussing after stopping down to f/5.6 or smaller. Again, the key is that you fully open the lens when auto focussing and close aperture after that. Any lens should by default behave like this on the Sony cameras. But they all don’t!

There is a basic AF adjust feature available. I tried it and yes it can adjust front- or back-focussing errors. In the end I reverted to the original setting and so far everything seems well. Especially when taking portrait shots, the AF is really super accurate.

Westerwald. (Sony A7 II with 90/2.8 at f/5.6)
There’s light on your path. Westerwald. (90/2.8 at f/2.8)

My conclusion: It’s a winner combo. Really!

Overall, I find that handling the lens on the A7 II is very enjoyable, despite it showing some weaknesses. I do have to stress again I’m not an action photographer. But the Contax G system was never made for super-fast action photography and the lens design shows. What I do see though is a super-high quality lens both regarding optics as well as mechanics. It’s a solid all metal construction that dates back to the glorious past. Also it features a very classic optical design – no modern aspherical magic stuff going on here.

It just oozes quality when you handle it. It makes you enjoy this quality and probably even calm down a bit during taking pictures. If you want speed, go somewhere else, but if you enjoy handling a really solid, beautiful lens on your camera, with even some modern comfort (AF) thrown in, this might be for you.

Oh, and the Contax G 90/2.8 lens is sharp. It does show color issues when open. I did not correct them in any of the shots shown here but that is because I sometimes even love those optical imperfections – as the overall picture still shows outstanding optical quality. It is textbook sharp. Stop it down to f/5.6 or so and there is – for my eyes, I did not take it to the labs :) – no optical fault at all, it is super contrasty and sharp into all edges, completely outresolving the 24 MP chip of the A7 II.

So we have beautiful optics, beautiful mechanics, and I especially like that it is a compact lens (also with a very compact adapter). It’s simply a beautiful lens on the A7 II. I enjoy it very much, including the Techart adapter that so far works flawlessly and never failed… with all the pictures on this site, I just used AF and it was spot-on. I hope it stays that way, and I might want to add the 35/2 or 45/2 to my Contax G lineup!

Cheers, Thomas

Restaurant "Te koop in Tilburg". (90/2.8 at f/2.8)
Restaurant “Te koop in Tilburg”. (90/2.8 at f/2.8)

2 thoughts on “Much more fun than expected – the Contax G 90/2.8 on the A7 II

Add yours

  1. Mine still crashes enough that it is unusable on the A7RII.

    What firmware version do you use on the adapter?

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