Zeiss Loxia 35mm and 50mm – Superb Performers

One of the biggest complaints the Sony full-frame mirrorless system has been receiving, is lack of good lens choices. With the launch of the Sony FE mount, Sony introduced only two high quality prime lenses in collaboration with Zeiss, the FE 35mm f/2.8 ZA and the FE 55mm f/1.8 ZA, both of which have been designed specifically for the short flange distance of the Sony A7 series cameras and have stellar optical characteristics. In September of 2014, Zeiss introduced two additional high quality primes for the Sony FE mount. Dubbed “Loxia”, these lenses are quite different from the Sony versions in a number of ways. First, they are both engineered and made by Zeiss, which means higher quality build and construction. Second, similar to many other Zeiss lenses, the Loxia line is manual focus only – and it is designed to be so. Third, they are also optimized for videographers, with a “DeClick” feature, which allows for smooth adjustment of aperture right on the lens. A number of our readers expressed interest in the Loxia lenses, so after having an opportunity to shoot with these gems, I was able to measure their optical performance in my lab. In this article, I would like to provide some information on the optical characteristics of the two Loxia lenses. Let’s start with the Loxia 35mm f/2:

Zeiss Loxia 35mm f/2 Biogon T*

The Zeiss Loxia 35mm f/2 feels nothing like the Sony 35mm f/2.8. It is noticeably heavier, has an all-metal barrel (vs plastic) and hood and feels completely different to handle. Unlike the Sony 35mm f/2.8, it has an aperture ring, so you control aperture directly through the lens (there is no way to do it through the camera). The focus ring is smooth and very responsive. The moment you start moving the focus ring, the camera goes into the zoom mode automatically, allowing you to get precise focus. Overall, it feels and acts like a much higher-grade lens than the Sony-made version. Let’s take a look at its MTF characteristics:

And here is the comparison with the Sony 35mm f/2.8:

Yup, we have a new center resolution champion – the Zeiss Loxia 35mm f/2 outperforms the Sony 35mm f/2.8 in the center at f/4. However, its mid-frame and corner performance are a bit disappointing due to field curvature, particularly when you focus at close distances. So if you focus at something flat like a wall, you might get really sharp center focus, but the mid-frame and the corners will look less sharp in comparison. As you focus towards infinity, field curvature diminishes greatly. And stopped down to f/5.6, it practically disappears – you can see that it matches the performance of the 35mm f/2.8 from there on. The second issue is focus shift, which was quite apparent when I was measuring the MTF performance of the lens. The good news is that focus shift for this lens does not matter, since you will most likely be setting aperture first, then focusing. But if you decide to focus once and change aperture, keep in mind that focus shift can result in focused area being slightly moved, resulting in unintended area getting in focus instead. Although I might sound like a Zeiss fanboy right now, but this is also not a big issue for this lens. Zeiss did not optimize the design the Loxia lenses to be ultra-sharp all across – the highlight of these lenses is the beautiful rendering of images, which they accomplish wonderfully.

The highlight of the Loxia 35mm f/2 is distortion, or lack thereof. Imatest measured pincushion distortion at 0.12%, which is even lower than on the superb Sigma 35mm f/1.4 Art! Vignetting is pretty noticeable at f/2, but stopped down it is reduced dramatically. Chromatic aberrations are well under control and Imatest measured at most over a pixel of CA. To be honest, I actually like the way this lens vignettes and I would personally choose not to remove it in post – for me, it is a characteristic of the lens rather than an optical issue.

A couple of image samples that will be published in the upcoming review:

Zeiss Loxia 50mm f/2 Planar T*

The Zeiss Loxia 50mm f/2 is another beautiful lens, which is crafted very similarly as the Loxia 35mm f/2. In fact, if you buy the 35mm f/2 for your Sony A7 series cameras, it makes sense to get this lens as well, since you will most likely fall in love with both. And here are the MTF numbers produced by Imatest:

And here is a comparison to the Sony 55mm f/1.8:

Once again, the Zeiss Loxia outperforms the 55mm f/1.8 in the center at f/4. However, just like the 35mm f/2, the mid-frame and the corner performance certainly suffer in comparison, especially at wider apertures. The Sony 55mm f/1.8 is better across the frame when stopped down though, so if you are looking for the best sharpness at most apertures, the 55mm f/1.8 is still the way to go. By f/8, both lenses are more or less the same in terms of sharpness.

The Loxia 50mm f/2 also suffers from field curvature and focus shift issues, but the problems are a bit less noticeable than on the 35mm f/2. To get the best out of this lens, I would still recommend to set the aperture first, then attempt to focus. At close distances, you are dealing with very thin depth of field, so you want to keep this in mind. As for field curvature, it is much less pronounced, but is definitely there when compared to the Sony 55mm f/1.8.

Distortion is also very well taken care of – Imatest measured -0.97 barrel distortion, which is not an issue and won’t be visible in your images. Vignetting is controlled very well. Slight vignetting is visible at f/2 and f/2.8, but almost disappears by f/4. Chromatic aberration is even lower than on the Loxia 35mm f/2, measuring at most half a pixel.

A couple of sample images:

With the two Zeiss Loxia lenses and the three newly introduced Sony FE primes, Sony’s line of high quality primes now consists of a total of 7 lenses. I am looking forward to seeing more high quality lenses like the Zeiss Loxia series and I am definitely anxious to see how the new 35mm f/1.4 performs compared to the above two 35mm lenses!