This is the Optical Design Department- Second Edition

Hello, everyone.

"This is the Optical Design Department" is a series that takes an in-depth look at LUMIX lenses.

In "This is the Optical Design Department", we in the Optical Design Department will explain the lens designs and their features, as well as the dedication and philosophy behind our work that you will not find in our catalogues or websites.

For those who are considering purchasing a camera lens, we encourage you to learn more about the design philosophy behind LUMIX lenses, and for those who already own a LUMIX lens, we hope you enjoy learning about the unparalleled attention to detail and thought that goes into the superb image quality you enjoy in your photography.

This is an article that explains various lenses written by developers full of technical jargon. By reading this, you too will be peering into the depths of enthusiasm for lens collecting.

The second article is about LUMIX S PRO 24-70 mm F2.8, explained by Kurioka.

This is the second full-frame mirrorless camera developed by Panasonic.

Large-aperture zoom lenses are a must-have for manufacturers, and even in today's mirrorless landscape, they are a popular choice for a variety of mounts. This means that you can see each manufacturer's particular area of focus by looking at these types of lenses.

If a manufacturer includes portrait or snapshot examples in their catalogues or on their websites, it likely indicates that their products are intended for photographing people. If image quality is highlighted, it suggests they have worked to improve resolution. If autofocus is mentioned, it shows an emphasis on high focusing accuracy and tracking performance.

Given that standard zoom lenses are likely to be carried around on many occasions, our goal was to design a lens that allows users to capture high-quality photos and videos across a variety of shooting conditions.

In developing this large-aperture standard zoom lens, we focused on optical performance in terms of resolution, bokeh, and chromatic aberration. Our aim was to create a lens that would be suitable for both still photography and video.

The lens is also designed for video recording, allowing you to experience smooth, fast focusing and quiet operation.

To achieve this goal, we spared no effort in using the finest components in the optical design. This has enabled the lens to deliver the very best in photographic and video expression, including outstanding resolution, colour reproduction, and bokeh effects.

Our goal was to obtain "Certified by LEICA" approval for this high-performance lens, and we delivered.

Passing LEICA's stringent approval criteria is a testament to the superior performance and quality of this large-aperture zoom lens.

This section will cover three points that were considered in the optical design.

Note, however, that it is inherently difficult to discuss the high performance of each component separately.

Therefore, I will only touch on the key technical points. The nature of optical design is such that the design solution is created by controlling hundreds of parameters through a methodical process of trial and error with the product in mind.

Let's take the curvature of a single surface of a single lens as an example of a parameter. This alone affects several performance factors. Optical designers refine the design solution by working closely with the development team to discuss various lens-related conditions, such as component specifications, assembly requirements, and target performance, and incorporate them into the actual design to achieve the optimal outcome.

The key technical features of this lens, defined through these discussions, are as follows.

This lens uses four ED lenses* to significantly reduce chromatic aberration. ED lenses are lens elements made of ED glass that cancel out the chromatic aberration that occurs on the blue side of the spectrum when light passes through the lens.

By concentrating the ED lens near the centre of the optical system, chromatic aberration is effectively suppressed from the wide end to the telephoto end of the standard zoom lens.

Improved chromatic aberration is not just a result of using ED lenses. These lenses are placed in areas where they can effectively cancel out the effects of chromatic aberration, which changes as you zoom in and out.

Chromatic aberration not only causes colour bleeding—it also affects resolution. Colour sensors divide the contrast into each of the RGB colours, and the less chromatic aberration there is, the better the resolution of the image after RGB division.

ED glass, the material used to make ED lenses, is relatively soft compared to other glass materials. This makes it difficult to process into lens elements, and optical designers must take this into account when using ED lenses.

Chromatic aberration suppressed by using ED lenses

This lens uses a double-focus system in which two sets of lenses move when focusing. The advantage of this system is that it can improve performance even when the subject position changes from infinity to close-up.

There are various performance factors to consider when choosing a focusing system, such as focusing speed, resolution, and shorter shooting distance. This lens, however, is specifically designed to enhance focusing speed and resolution.

Focusing involves changing the distance at which the lens is in focus. However, when designing a large-aperture zoom lens using a conventional single-focus system, it becomes difficult to maintain the image plane flatness* required to clearly capture the periphery of the image when focusing on a close-up subject. This means that it becomes difficult to achieve both focusing and image plane flatness.

The flatness of the image plane also affects bokeh. There may be times when you want to take a sharp photo of the main subject and subtly blur objects at different distances from the main subject. The flatness of the image plane makes it easier to take such photos, as objects at the same distance as the main subject will be in focus and objects at different distances will be blurred in proportion to the difference in distance.

This lens uses a double focus system, which has enabled the lens to achieve a high level of balance between these two effects: focus shift and maintaining the flatness of the image plane.

The lens also addresses the issue of breathing, which affects video quality. Breathing is a phenomenon in which the size of the image passing through the lens changes as the focus lens moves. Technically, it is necessary to align the position of the arriving light. In this respect, we were also able to use the high aberration correction capability of the double focus system to improve image quality by suppressing breathing.

There are other advantages to the double focus system: splitting the focus lens into two allows each lens to be lighter.

A lighter lens enables faster focusing, making it easier to track the subject. This is particularly advantageous in still photography and video, where the subject must be kept in focus at all times.

What's more, the actuator that moves the lens can be made smaller, which is another advantage.

Double focus system

However, the double focus system also has its weaknesses. To move multiple components in sync, they must be able to accurately determine each other's position at high speed and move as intended. To get the most out of the lens in different shooting conditions, this lens electronically controls the two lenses in tandem.

This linked control technology is the result of combining LUMIX's expertise in electronic control with advanced optics. It is a technology that has been cultivated in the Micro Four Thirds format and later expanded and implemented in the full-frame format.

Detailed depiction achieved through high resolution

Soft bokeh effect

This lens uses a seven component zoom to improve performance, and all seven lens groups move when the lens is zoomed.

Optical designers classify the focal lengths of each lens group as positive (+), negative (-), or non- power (0) to categorise the moving lens groups. This lens features a positive-negative-positive- positive-negative-negative-positive configuration.

Our Micro Four Thirds lenses use a positive-negative-positive-negative-positive configuration, but this lens has two more groups and has evolved significantly as an optical system. Compared to the Micro Four Thirds format, the larger size of the full format makes it harder to ensure performance at the same close range. If we want higher performance, we have to find ways of achieving it.

One of the reasons for increasing the number of lens groups from five to seven is that, as mentioned in b, we have added an extra lens group, mainly for focusing. Another challenge is to improve performance.

Among the seven lens groups, there is a section where positive lens groups are placed side by side. (Can you see them?)

We knew that splitting them would be effective in correcting aberrations, but it would have a significant impact on performance and would also be difficult to manufacture.

As I mentioned at the beginning, there are hundreds of parameters that affect performance, and this is a very high level of impact. Through repeated simulations and prototyping, we were able to enhance the level of perfection by working with the mechanical design team, the manufacturing methods, and the production facility. This enabled us to successfully bring the product to market.

There are many different variations in lens design.

The question is, how do you arrive at a design solution from all these options? One of the perspectives that LUMIX takes is to "see things from the creators' point of view".

This lens was created by incorporating the opinions of actual users and the kind of attention to detail I just mentioned.

This is one of the 'big three' standard zoom lenses. It is a popular model, so there are probably a lot of people who already own one. Whether you already have one or are thinking of getting one, we recommend that you give the LUMIX S PRO 24-70mm F2.8 a try.

One of the 'big three' standard zoom lenses packed with attention to detail

This article has provided an overview of the optical design of the LUMIX S PRO 24-70 mm F2.8.

If you already own this lens, we hope you will take note of the attention to detail in the images described in this article when you take your photographs.

If you do not, we hope you will give it a try.

We remain committed to introducing lenses that showcase LUMIX's meticulous attention to detail.

There are still many lenses we are eager to talk about! Stay tuned for the next article!