How the 100 mm F2.8 MACRO Became the World's Smallest and Lightest Macro Lens*
Hello, everyone. We are the development team behind the LUMIX S 100 mm F2.8 MACRO lens.
We are delighted to introduce the LUMIX S 100 mm F2.8 MACRO, the first 1:1 macro lens in the full-frame LUMIX S series.
It is also the world's smallest and lightest* macro lens in its class. With an overall length of approximately 82.0 mm and a weight of around 298 g, it achieves a size close to half that of conventional full-frame macro lenses. LUMIX users would recognise it as being similar in size to the F1.8 series.
In this article, we will explore the technical background that made the world's smallest and lightest* design possible, the optical considerations that went into the lens, and the key features highlighted by the development team.
Contents
◼ The inspiration behind the "compact and lightweight macro lens" concept
◼ The dual-phase linear motor that enabled the lightest-weight design
◼ The challenge of adopting three aspherical lenses
◼ Development team members share their favourite features
◼ A deluxe macro lens that surpasses the F1.8 series
The inspiration behind the "compact and lightweight macro lens" concept
Yoshikawa (Mechanical Design Team)
As shown in the LUMIX lens lens roadmap, the development of a 100 mm macro lens was already under consideration. Consequently, the development team held extensive internal discussions about how to achieve this goal.
During that time, the F1.8 prime series was released one after another, receiving positive feedback from users. This led to conversations about producing something within the prime line-up that is similar in size to the F1.8 series.
However, the reason the F1.8 series is so popular is that all the lenses share the same diameter and the same overall length. If we were to create something that was not identical but merely similar in size, we wondered whether it would deviate from the original concept. That was the dilemma.
The question then became: how could we make a macro lens the same size as the F1.8 series? Exploring this idea and working through the design and development required to achieve it is what led to the creation of this lens.
During the early to mid-development stages, we worked under the assumption that although we could match the lens diameter, the overall length would need to be a little longer; otherwise, it would be difficult to realize. Even so, we had a slight sense that sooner or later we would be told to “make it the same size as the F1.8 series” (laughs).
The goal of matching the F1.8 series was a 40% reduction in overall length compared with competitors' products.
Although a general solution for downsizing had already been identified, the entire team recognised that there were still significant challenges to overcome before the lens could be brought to market.
The key point was making the lens the same size as the F1.8 series. We felt that extending the overall length by even five millimetres would considerably reduce the complexity, but we moved forward with the determination to achieve it for the benefit of our customers.
Five millimetres may sound small, but in design terms it provides a great deal of leeway. Although the construction diagram appears to show empty space, the interior is tightly packed with components, including the double-focus mechanism, which enables its full range of movement.
The dual-phase linear motor that enabled the lightest-weight design
While previous lenses used voice coil motors (VCMs), the new 100 mm F2.8 MACRO employs a dual-phase linear motor.
Both the VCM and the dual-phase linear motor make use of Fleming's left-hand rule, whereby force is generated when current flows through a conductor within a magnetic field. In the conventional VCM, the arrangement of the magnets meant that thrust could only be produced by part of the coil. As a result, when attempting to move a large lens element, multiple VCMs were required due to insufficient thrust, increasing lens size and weight.
The dual-phase linear motor addresses this by using multipolarised magnets, allowing almost the entire coil to be utilised to generate thrust.
In addition, it uses a unique configuration in which magnets are positioned opposite each other on both sides of the two-phase coils. By establishing a control technology that switches between the two coils depending on position while supplying current, the motor can operate smoothly and continuously across the entire range.
Conventional VCM: There is only one force-generating section, shown in red, resulting in poor efficiency
Dual-phase linear motor: The magnets are multipolarised to efficiently generate force
This enables a force output that is approximately three times greater than that of conventional lenses of the same size, leading to a compact and lightweight design.
In terms of lens design, the conventional VCM weighed around 80 g, whereas the dual-phase linear motor weighs just 29 g, achieving a weight reduction of over 50 g simply by switching to the new motor.
Downsizing the motor significantly eased the complexity of the optical barrel design configuration, greatly contributing to reducing the lens's diameter and weight.
One reason the total weight comes in under 300 g, at 298 g, is probably the use of the dual-phase linear motor. However, this may only appeal to those who are particular about every gram (laughs).
Background to the development of the dual-phase linear motor
Fujinaka (Dual-Phase Linear Motor Development Team)
In fact, around twenty years ago, I worked in Panasonic's motor development division, where I was involved in creating new types of motors.
Due to my background in this area, I had realised quite some time ago that conventional VCMs could be downsized by multipolarising them.
I knew this, but there were many twists and turns before the technology could actually be implemented in a product.
When development of the S series began, marking LUMIX's entry into full-frame cameras, one of the goals was to enable the focus-driving components, including the lens, to be driven with several times the force of conventional designs. It was at this stage that I first proposed the technology that would become the basis of the dual-phase linear motor.
We then perfected the fundamental technologies for the dual-phase linear motor, including techniques to minimise force fluctuations by refining coil shapes and positioning magnets on either side of the coil. Patents for these technologies were registered in Japan and the US in 2023.
My prior experience in motor development played a significant role in this project.
However, there were still numerous challenges to overcome before the technology could be integrated into products. These included not only designing the motor itself, but also developing the control technology required to operate it at high speed, with high precision, and quietly.
At the time, Panasonic was launching various new LUMIX cameras and lenses, which made taking on the development of new control systems quite challenging.
So, to be blunt, although the prototype for the dual-phase linear motor had been completed, the years passed without us being able to develop the control technology needed for product operation. The prototype we had created back then had been left untouched for more than two years (laughs).
When the decision was made to commercialise the 100 mm F2.8 MACRO, I believed that a dualphase linear motor was the only way to achieve a compact, lightweight design. I convinced my superiors to let me get involved in developing the control system so that we could bring the lens to market.
Cross-section of a dual-phase linear motor
As a result, we were able to confirm that the prototype, which had been left unused for almost two years, could now be controlled without issue and delivered performance almost exactly as designed.
Although the technological development had finally reached a level where it could be implemented in a product, another challenge emerged. Put plainly, it was a matter of cost.
While conventional VCMs are larger and heavier than dual-phase linear motors, their performance is well established, and they are widely used in products. The question became whether we should now invest in incorporating them into new products, despite the additional costs.
The cost concerns came from various angles: the increased number of magnets required for the motor, the increase in microcontroller programme capacity leading to higher material costs, and the development costs associated with integrating new control technology into the microcontroller.
These various factors raised concerns about a potential increase in cost, and, to be frank, there were voices opposing the idea.
However, by repeatedly explaining to the team the added product value that would result from incorporating the technology and by engaging in various negotiations, such as cost-reduction discussions with material suppliers, we eventually secured the agreement of the relevant members. As a result, we succeeded in bringing the lens into mass production. It was really tough going (laughs).
In the end, we managed to equip the 100 mm F2.8 MACRO with the dual-phase linear motor, reducing its size and weight. I feel this has significantly enhanced the value of this compact, lightweight macro lens, which is its greatest feature.
The challenge of adopting three aspherical lenses
Suzuki (Optical Design Team)
Using three aspherical lenses in the medium telephoto macro category was probably a rather challenging endeavour.
Typically, lenses in this category have either no aspherical elements or just one. However, because the design began with the prerequisite of achieving the "F1.8 series size", we believed that without adopting aspherical lenses, it would be impossible to realise the 100 mm F2.8 MACRO.
For a macro lens that is compact yet uncompromising in image quality, three aspherical lenses were essential.
The arrangement of the lens elements within the barrel essentially involves correcting aberrations. Although you may have seen a cross-section of a barrel containing both convex and concave lenses, the design of this lens was so compact that combining these elements was impossible. To maintain performance while fitting everything inside the barrel, we incorporated aspherical elements into an efficient design.
Also, when people familiar with cameras hear that three aspherical lenses are used, they might expect pronounced ring-line bokeh, also known as 'onion bokeh'.
However, the 100 mm F2.8 MACRO has been designed to minimise this effect, drawing on the technology LUMIX has developed over the years. This allows us to take full advantage of the benefits of aspherical lenses and achieve both compactness and high image quality.
Internally speaking, we have spent many years developing compact prime lenses and advancing our aspherical lens technology. After thoroughly examining the risk of ring-line bokeh appearing when using aspherical elements in macro lenses, we concluded that our current technical capabilities could overcome this challenge. This underpinned our decision to pursue the compact size used in this model.
Development team members share their favourite features
Its compact size goes without saying, but there are several other noteworthy points. Here is a brief overview:
[1] Reduced lens breathing
When focusing in the macro range, a slight change in the angle of view (lens breathing) tends to occur with typical macro lenses. However, the 100 mm F2.8 MACRO has been designed to minimise this effect. This should also eliminate the need to reposition the tripod after focusing to adjust the composition.
[2] Soft bokeh
As mentioned earlier, the use of three aspherical lenses can increase the likelihood of aberrations and distortions appearing in images. However, we have addressed these issues while designing the lens to produce the softest possible bokeh.
[3] Updated focus ring
Although this lens shares the same exterior design as the F1.8 series, the focus ring has been specifically updated for macro photography. When using manual focus with a macro lens, particularly in MF Linear mode, achieving accurate focus requires very fine adjustments. With the ring structure used in the conventional F1.8 series, even slight movements could cause the focus to shift noticeably. For this reason, the focus ring has been redesigned to allow much finer control over focus movement.
[4] Slightly greyer lettering
The colour of the lens information printed on the lens surface has changed from white to a slightly grey colour. This change was first implemented with the LUMIX S 14-28 mm F4-5.6 MACRO. Since 1:1 macro and wide-angle macro photography often involve shooting very close to the subject, this adjustment helps ensure that the printed markings are less likely to appear as reflections on the subject.
[5] Compact yet equipped with a distance selector switch
Adding a switch after the overall size had already been defined was quite challenging, especially because incorporating a three-way switch required significant effort. While incorporating a simple two-way switch for the full and macro ranges would have been straightforward, we opted for a threeway switch to accommodate different subjects, such as portraits. This enables switching from infinity to 0.5 metres. Integrating the switch and its markings into this external profile was a considerable challenge.
A deluxe macro lens that surpasses the F1.8 series
Although the concept was a macro lens with the same size as the F1.8 series, the development team considers the internal design to be completely different.
The previous F1.8 series lenses were not particularly suited to close-up photography, and many creators had expressed the desire for a lens that could focus even closer.
We feel truly fortunate, therefore, to have developed this 1:1 macro lens while retaining the unique workflow and ease of use characteristic of the F1.8 series.
Enjoy the mobility of the world's smallest and lightest* macro lens for stress-free macro photography!
*Among full-frame mirrorless AF-compatible interchangeable lenses, those with a focal length of 90mm or more that are 1:1 macro lenses. As of January 9, 2024. According to Panasonic.
