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30 Days of Batis 2/40 CF
A Batis adventure and a personal photography scratch book with a creative touch.
Sharing a new post every day for the next 30 days.




Day #39 - a small interview with Dr. Michael Pollmann from ZEISS

Toni Ahvenainen

Sony A7III & ZEISS Batis 2/40 CF – f/2.0, 1/400sec, ISO100, raw Photograph by Toni Ahvenainen

Sony A7III & ZEISS Batis 2/40 CF – f/2.0, 1/400sec, ISO100, raw
Photograph by Toni Ahvenainen

Surprise, surprise! Today I have a small interview with ZEISS for you! I planned this interview from the beginning of extra 10 days and I finally got the answers for the questions I wrote some time ago. I got to interview Dr. Michael Pollmann who is responsible "category management" at ZEISS. He's taking care of what ZEISS should bring into different lens families and what strategic decisions ZEISS should make regarding category management. With his clean white lab coat and Abbe's refraction index table in the hand Dr. Pollmann kindly came from the ZEISS's simulation lab filled with Cray super computers and paused his research for abstract geometrical aberration curves in physical image formation including the spectral response and quantum physics – to answer some questions for the mortal people. Nah, just kidding a bit here! The ZEISS physicists and optical engineers are not stereotypical scientists, nor is ZEISS HQ the ivory tower above the real world. Instead they are very easy to approach and friendly with their feet on the ground, and Mr. Pollmann agreed with the interview right away when I asked for it. And they don't wear white lab coats at ZEISS – hmm, I think they don't...  

Anyway, here's the small interview which deals with the Batis 2/40 CF design concept, image quality and the new firmwire-update. You're welcome!

1. ZEISS successfully launched the new ZEISS Batis 2/40 CF at September 2018. Now, one of the most surprising point of this new and anticipated Batis lens is the unique 40mm focal length. Could you share some of the reasoning why ZEISS decided to choose this particular focal length and not 35mm or 50mm for example?

The idea was to bridge the gap between the ZEISS Batis 2/25 and the Batis 1.8/85. Of course, our first reaction was “let’s go for a 35mm and a 50mm.” However, the question arose whether this would be the smartest approach for the user. They would often have to decide which one they like better. So we thought: Wouldn’t it be more beneficial to have one lens that combines these two types, building a perfect set together with the 25mm and the 85mm models? That was the moment the Batis 40mm was born.

2. When I tested the Batis 2/40 CF I found it has amazingly consistent optical performance, not only  across the whole frame, but also throughout the whole focusing range from close range to infinity. In other words, the Batis 2/40 CF holds it performance very well in a very different shooting scenarios which is, one could say, a particular character of this lens. Could you say this was a special design target for the Batis 2/40 CF?

You are absolutely right! But it was not a special design target for the Batis 2/40 CF exclusively, it’s the design target for the whole Batis family – and the rest of our lens portfolio. Image quality is the most important feature for our customers. We act on the assumption that they don't want to compromise on image quality. For us, that includes a high image quality level under all circumstances, especially a very homogeneous quality level across the complete image field and focusing range.

3. However, since the release there have been some bumps in the road too. There was a particular issue with the Eye-AF which, in some situations, led to a bit front focused pictures, especially at the close ranges. The Eye-AF is course a very important function in the Sony Alpha cameras and this issue has caused disappointment for some of the early users. Could you tell us something about this issue and how it was solved?

The Eye-AF issue is an example of "hindsight is 20/20." We checked the AF accuracy and repeatability in all the standard AF settings – AF-S, AF-C etc. – prior to the market launch. The lens worked perfectly. In principle, when using Eye-AF, the communication to the lens is no different from “standard” AF-modes. The camera decides the best focus lens group position. However, in this case, they were visibly different. So we fine tuned the lens control parameters, and now the Eye-AF works fine. And you can be sure that, in the future, the Eye-AF will be tested with every new lens prior to bringing it to market!

4. It’s good, that it’s now fixed. Does it work on all Sony cameras?

Definitely! We have tested it on all full frame E-mount and also the current APS-C E-mount cameras. The results have been positive: there's no difference to other Batis or similar Sony lenses.

5. The new FW-update also addresses another aspect of the lens, the aperture behavior at the close focus range. Now, this is not an issue and the lens has been designed to work that way so that the aperture closes down a bit when working at the very close focus distances under a 1 meter. Could you explain a bit about this design decision?

When we decided to go for a 40mm lens, the idea was to get a lens that is more versatile than a 35mm or a 50mm, individually. But wouldn’t it be great, if it would be more versatile than both lenses together? What’s missing for “normal” standard focal length lenses? The chance to get really close to your subject! So the close focus was a major feature of the lens concept. And our plan was not to compromise image quality. We wanted a high level of image quality all the way down to minimum object distance.

During the optical design phase, it became evident that keeping the aperture constant would have made the lens a lot bigger and heavier – and more costly. This would have contradicted the basic concept of a very versatile lens as well as the general concept of the Batis family. Back then, we decided to automatically stop down the aperture close to minimum object distance to ensure exceptional image quality even at close range.

6. The new FW-update also changes the aperture behavior a bit at close ranges. The aperture now closes down less at the close focus ranges, which also leads to be better out-of-focus highlight rendition. Does this change compromise the image quality, or is this just a way to optimize the lens behavior?

We’ve now tweaked the lens characteristics so that the aperture can be kept more open while still ensuring high image quality. The lens now stops down only 1 stop at max, and only for minimum object distance. Also, the focus distance, where stopping down starts, was reduced to 0.65m. Thus the highlight rendering should now be unaffected by the aperture behavior for typical portrait shooting distances.

7. This sounds like a very good update for the Batis 2/40 CF and I'm sure many users are happy to see the FW-update to arrive finally. If I'm not mistaken the Eye-AF issue and aperture behavior at close distances caused some confusion at the release, but I'm sure now that the Eye-AF issue is fixed and the aperture behavior is optimized (and also better understood), the Batis 2/40 CF will soon take its place among the other Batis-lenses.

The Batis 2/40 CF had its place within the family right from the start. From the beginning, there was considerable interest, and our production area had to work hard to meet the demand. We take the users’ feedback seriously and hope that, with the FW update, those lens owners who struggled with the two issues are now satisfied. The issue with the Eye-AF was unexpected. We are sorry for any inconvenience or annoyance. We have taken countermeasures so it won’t happen again in the future. 

Closing the aperture is a bit different as this was a deliberate decision on our part. We would like to apologize in two respects: first, for not having communicated this behavior right from the beginning. We didn't include the rationale behind our decision in the marketing material. We have reviewed our processes, and marketing material will include more explanations about product decisions from now on.

Second, we would like to apologize for the speed of our communication after the two issues occurred. Our aim was to give our customers valid feedback. Therefore, we carefully checked how to address the questions raised. This took us some time and, unfortunately, some customers felt this meant we didn’t care about these topics. You can be sure – customer opinion and customer feedback are crucial for us. If some functionality of our lenses is questioned, we look into it extensively. We will strive to be faster in our communication with the community in the future, also as concerns answering questions and complaints.

8. This sounds very good, and where can the new Batis 2/40 CF FW-update be found?

The FW-update, together with update instructions, can be found on the ZEISS website. It's free for all users, and we recommend updating to the new version of the Batis 2/40 CF. It can be done easily with Sony cameras. If someone needs help, they can contact our Customer Service Team ( for additional support. It is very important to us that everyone can update their Batis 2/40 CF lenses and enjoy them without any further issues.