Many users of the Sony A7, A7S, A7R, and A7II have the Sony Sonnar 55/1.8 ZA standard lens. Some are also wondering about the Loxia Planar 50/2.0 that I wrote about previously. An alternative is the Contax G 45/2.0 which had a very good reputation for users of Contax G1 & G2 film cameras.

Using the Contax G lenses on the E-mount of the Sony NEX / A7 requires an adapter. I’m using the Metabones adapter shown on the pictures. The Metabones is fully manual without any electronic couplings whatsoever. An electronic adapter with (slow) AF is also available from DeoTech.

On the ergonomics side, the Contax G 45/2.0 has a mechanical aperture ring (1 EV increment only) and focus is through an AF screw rotated by the Metabones adapter. There is no distance scale. Filters are for 46mm diameter. The lens is very small and almost « cute ».

The Contax G 45/2.0 is very compact but after adding the Metabones adapter, it becomes only slightly more compact than the Loxia 50.

The Contax is also the lightest but weights even out when adding the adapter.

Weights, including filter, caps, and hood:

Contax G 45/2: 215g

Contax G 45/2 + Metabones: 357g

Sony FE 55/1.8 ZA: 353g

Loxia 50/2: 374g

Focus with the Metabones adapter is reasonably smooth but fitting the adapter is a bit tricky as shown in this video

Three area of the Paris city hall are used to compare the thee lenses. No tripod was used and light conditions varied a little bit between the shots.

At F2.0, all three are very sharp in the center, with the Contax slightly behind. But in the corners, the Contax is very mushy.

Click the pictures for 100% pixel size.

At F2.8, there is a slight improvement for the Contax, but the Sony & Loxia are already seriously sharp.

The Contax gets better at F4.0 but still far from its younger brothers.

Corner sharpness finally becomes good for the Contax at F5.6.

The F/2.0 aperture allows to blur the background but the lens lacks the « smoothness » of longer focals such as 85/1.4. Especially, the outlines are quite visible in the circular highlights.

The cat’s eyes are reduced at F/2.8.

The Sony Sonnar 55/1.8 ZA and the Zeiss Loxia Planar 50/2.0 are very sharp even wide open. The Contax G Planar 45/2.0 is also quite sharp but only on the center & mid-frame between F2.0 & F4.0, full frame sharpness is achieved from F5.6 onward.

On the whole, the Contax G Planar 45/2.0 is still quite good for it’s size & age, especially since it costs around 300/350€ on the 2nd hand market. The Sony Sonnar 55/1.8 ZA and the Zeiss Loxia Planar 50/2.0 are both very good, choosing either is more a question of shooting style and ergonomics.