The Ultimate Guide to the SONY Distagon T* FE 35mm F1.4 - Optical Design Value Analysis No.058

This is a performance analysis and review article of the Distagon T* FE 35mm F1.4.

You hardly understand the specific differences in how the lenses work and how their performance differs from each other, do you?

Even if you look it up in magazines or on the Internet, all you will find are similar "word-of-mouth recommendations" and articles like that.

In this blog, while researching the history of lenses and their historical background, we estimate lens design performance based on patent information and actual shooting examples, and analyze lens performance in detail from a technical viewpoint through simulations.

Professional lens designer Jin Takayama will carefully unravel optical characteristics such as optical path diagrams and aberrations, which are generally not visible, and explain the taste and descriptive performance of lenses in a deep and gentle manner.

Now, please enjoy the special information that you can read only on this blog in the world.

Overview

The SONY FE 35 mm F1.4 ZA is a large aperture wide angle single focus lens with the ZEISS inscription for the SONY mirrorless single lens FE mount.

As you know, SONY FE lenses are divided into 4 grades.

ZEISS (ZA,Z)
G Master (GM)
G
Unnamed

This lens has been given the inscription of ZEISS, a famous optical manufacturer in Germany.

The relationship between ZEISS and SONY was mentioned a little in the article of SONY FE50mm F1.4 in the past, so please refer to it.

Private Memoirs

The title "Distagon" in the product name comes from the name of a wide-angle high-performance lens developed by ZEISS in the 1960s.

This Distagon was created in the early days of computer-aided optical design. It is a lens that achieved ultra-high performance due to the computing power of a computer, despite having a dramatically complex lens structure.

According to one theory, in the early days of computers, it was optical design that enjoyed the greatest benefits of computers in industry.

Optical design is a kind of calculation work that tries to calculate the path of light passing through a lens a huge number of times, and gradually pushes it into a lens shape with less aberration, so it is exactly the best work for computers.

By the way, the first domestic computer in Japan is said to be "FUJIC," which was produced by "Fujifilm" in 1956 "for optical design."

Although this FUJIC was paid for by the company, it is said to have been produced almost on an individual level, and it is a pity that it has not seen the light of day much, probably because it was born too early.

Fujifilm is a large company that continues to exist today, but if the company had developed in the direction of computers based on FUJIC, it might have become a company like "IBM" or "APPLE," so even if there were excellent engineers, it would be difficult to manage a company.

However, Fujifilm's main business now (2021) is medical equipment and industrial materials. It was originally a camera and film company, but now it is developing like a phantom, so it cannot be read as a corporate development.

Document Survey

A search of the patent documents shows that WO2016/056310 is a related document.

However, this lens has the name of the famous German manufacturer ZEISS, but the inventor in this patent document is "pure Japanese" as the name, and "super major Japanese manufacturer" seems to be the right holder.

The name Tuice is not mentioned in the literature, and it is written in very fluent Japanese without a hint of German.

Then, this lens follows the famous reasoning of the past.

It is the same method as SONY FE 50 mm F1.4 ZA. I will say it is a pattern designed by a person who "trained in Germany" after returning to Japan!

More than that, it is dangerous to speak out. Let's follow the wisdom of our predecessors, "The wise do not approach danger."

Now, assuming that Example 3, which has a similar shape, has been commercialized, the design data will be reproduced below.

Notes!

The following design values have been selected and reproduced from the appropriate patent literature and do not correspond to the actual product. Naturally, the data is not guaranteed, and I am not responsible for any accidents or damages that may occur by using this data.

Analysis of Design Values

Optical Path Diagram

Above is the optical path of the SONY Distagon T * FE 35 mm F1.4 ZA.

The lens configuration consists of 8 groups of 12 lenses and 3 aspherical lenses, and the intention is to completely eliminate spherical aberration peculiar to large-diameter lenses.

However, it is difficult to explain what kind of shape "Distagon" refers to in the first place.

The order of convex and concave lenses is fixed in the double Gauss configuration, but the number of lenses in the Distagon configuration is also large, so the shape is not strictly defined.

As for the impression of the Distagon configuration, I recognize it as "an asymmetric wide-angle large-diameter lens with a series of concave lenses on the subject side," but this lens is one of those with a strong concave lens on the subject side.

As the world's first 35 mm F1.4 lens for mirrorless single lens, it can be said that the shape is quite unique.

In the future, when the same specification lens for mirrorless single lens of each company comes out, you may understand the greatness of this lens more.

Longitudinal Aberration

Graphs of spherical aberration, image surface curvature, and distortion

Spherical Aberration , Axial Chromatic Aberration

Let's take a look at the spherical aberration. It is a straight line that is almost disgusting.

Around 30 years after the MINOLTA AF 35 mm F1.4, which was a radical product at the time, this lens was born as the world's first mirrorless single-lens lens. This level of performance is a matter of course because it was required to have overwhelming performance.

The axial chromatic aberration is also well balanced.

Field Curvature

There is a slight difference between the sagittal and tangential directions of the field curvature at a height of about 12 mm in the middle of the screen. This is a concern, but it is necessary to determine the final characteristics using the MTF.

Distortion

The distortion is like a wide-angle lens with a graph shape that is slightly tilted to the minus side, and when you take a picture, it becomes a cask-shaped.

It's not that you feel strange when you take a picture like this, but you may not notice it depending on the setting of the camera because recent cameras are corrected by image processing.

Lateral Chromatic Aberration (Magnification Chromatic Aberration)

The lateral chromatic aberrations is not at the level of being large, but the bulge at around 10 mm image height in the middle of the screen may be slightly noticeable with a small aperture, but this lateral chromatic aberrations is also corrected by image processing, so you may not notice it depending on the camera settings.

Transverse Aberrations

(Left)Tangential direction, (Right)Sagittal direction

Let's look at it as Transverse Aberrations.

The coma aberration in the tangential direction and the coma flare in the sagittal direction seem to be dramatically less compared to the large diameter lens.

As shown in lateral chromatic aberrations, when you look at the chromatic aberration components such as C line (red) and g line (blue) in the tangential direction, if the image height exceeds 18 mm in the peripheral part of the screen, you will feel the pain peculiar to large-diameter wide-angle lenses.

Spot Diagram

Spot Scale 0.3 (Standard)

This is the result of an optical simulation, but first let's look at the spot diagram.

With the spot scale for standard evaluation, it is corrected to almost the point size, and you will not feel aberration in the whole screen area in general shooting.

Spot Scale 0.1 (Detail)

MTF

Maximum Aperture F 1.4

Finally, let's look at the results of the MTF simulation.

The MTF peaks are sufficiently high, and the positions of the peaks match, indicating that the image quality is uniform down to the periphery of the screen.

The SIGMA 35 mm F1.4 dg HSM that we analyzed in the past was released in the near future, but at a glance, the SIGMA has high performance in the center, and the SONY has high homogeneity in the periphery.

I would like to make a detailed comparison article at a later date.

Small Aperture F4.0

Conclusion

Now, about 30 years have passed since the world's first 35mm F 1.4 autofocus lens was created by MINOLATA. This lens has been fully renewed by Sony, and it has been found that it has achieved dramatic improvements in performance.

It is also the world's first lens with 35 mm F1.4 specifications for mirrorless single lens, and there is no doubt that it is a lens to embody the high performance of wide-angle lenses, which is the advantage of mirrorless systems.

I was overwhelmed by the high performance that did not go against the purpose.

Sample Picture

Example photos are in preparation.

If you are looking for analysis information on other lenses, please refer to the table of contents page here.

Analyzed LENS List "HERE"