Hi everyone, thanks so much for checking out my guide on adapting Carl Zeiss Pro-Tessar lenses to the Sony E-mount system.

I’ve already put together a few videos demonstrating these classic lenses on Sony mirrorless bodies, and there’s plenty more to come! I'll also be continuously updating the image gallery here as I roll out new Pro-Tessar lens reviews.

In my first video, I walk you through the specific adapter required and its unique quirks. My second video takes a deep dive into the mechanical and optical performance of the Carl Zeiss Pro-Tessar 35mm f/4.0 (originally for the Zeiss Ikon Contaflex), shot entirely on a high-resolution Sony A7R IV.

Mechanically, these Pro-Tessars are pure metal and glass. Because they were designed as a convertible lens system, they don't have a built-in focusing helical or an aperture iris. On the original analog Contaflex cameras, those elements lived in the fixed rear group—now, the adapter handles those duties. This minimalist design makes the front elements incredibly rugged; they truly feel like they were engineered to survive anything.

I just love the vintage aesthetic and the heavy, mechanical feel in the hand!

Lens Separation: What Is It and How Does It Affect Performance?

A well-known weakness among vintage optics is lens separation. The Carl Zeiss Pro-Tessars are unfortunately not immune to this issue, and my own 35mm f/4.0 copy is affected as well.

But what exactly is lens separation?

Camera lenses are made up of individual optical elements that are either free-standing or bonded together into groups—which is where specs like "9 elements in 6 groups" come from. To join individual elements into a single group, a specialized optical adhesive known as lens cement is used. Over the decades, this cement can dry out, crystalize, or fail, usually starting at the outer edges.

This creates a distinct, shimmering visual effect that looks very much like oil on water. In most cases, mild separation is largely an aesthetic issue with minimal impact on image quality—unless the cement degrades entirely, causing the elements to misalign or completely detach.

Mechanical and Optical Performance of the 35mm f/4.0 First introduced in 1956, the 35mm f/4.0 lens reviewed here comes with the following key specs: it weighs in at 236 grams, measures 6.5 cm in length, and has a maximum diameter of 6 cm. Up front, it features a 49mm filter thread. Thanks to its unique design as a convertible lens system, the front element and filter thread remain completely stationary and do not rotate when focusing.

Optical and mechanical quality of the 4.0 35mm:

The lens calculation dates back to the 50s of the last century and I used the lens on a 60 megapixel camera, the Sony A7rIV.

It performs surprisingly well for this. However, the sharpness at open aperture is not satisfactory over the entire image field and the corners of the image stand out again, unfortunately not in a positive sense. It looks better stopped down one stop. A significant increase in performance can be seen at f/8, although the image corners are not sharp even at f/11. The maximum imaging performance is achieved at apertures 11 and 16. Stopping down further to 22 or 32, however, produces significantly poorer results due to diffraction blur. If the image corners are not important, are outside the depth of field and are only focused on the image center, you can use the lens from aperture 5.6, better 8, without hesitation.

The distortion is corrected very well, so that it rarely requires post-processing.

Unfortunately, I was unable to achieve aperture stars with this lens, but depending on the lighting situation, I was able to achieve a soap bubble bokeh.

Depending on the subject, vignetting is clearly visible. Even at aperture 11, this is still visible and requires software correction if it is perceived as disturbing.