This is the Optical Design Department- Tenth Edition [LEICA DG VARIO-ELMARIT 12-35mm/F2.8 ASPH./POWER OIS]
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 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 LUMIX lens, we encourage you to learn about the design philosophy behind LUMIX lenses, and for those who already own a LUMIX lens, we invite you to discover the passion that has gone into creating its superb image quality.
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 lens buying addiction.
The 10th article is about LEICA DG VARIO-ELMARIT 12–35 mm F2.8 ASPH. POWER O.I.S., explained by Zaitsu-san.
Contents
◼ How the Mark III Lens Was Commercialised
◼ The Evolution of the Standard Lens in the Big Three Micro Four Thirds Line-up
◼ Evolution into a LEICA lens
◼ Suppression of Ghosting and Flare
◼ Enhanced Colour Reproduction
◼ Reduced Minimum Focusing Distance
◼ Optical Design
◼ Compact and Lightweight Design
◼ Video Recording Performance (Suppression of Lens Breathing)
◼ Lastly
◼ Photos Taken by the Author
How the Mark III Lens Was Commercialised
The Micro Four Thirds system was first introduced in 2008. Thanks to its portability and excellent mobility, it quickly gained widespread support from users and, at one point, even achieved the number one position in Japan’s lens mount market share by unit volume.*
Panasonic was the first company in the world to release a Micro Four Thirds camera. As the user base grew, the LUMIX lens line-up expanded to 28 models by February 2025.
LEICA DG VARIO-ELMARIT 12–35 mm F2.8 ASPH. POWER O.I.S., the standard lens of The Big Three zoom lenses, was commercialised as the Mark I and Mark II models.
In this article, we will look at the Mark III, which was released under the LEICA brand to further enhance the lens's performance and appeal.
The Evolution of the Standard Lens in the Big Three Micro Four Thirds Line-up
The Mark I was released in 2012.
It has a 35 mm equivalent focal length ranging from 24 mm to 70 mm and a constant brightness of F2.8. It is designed for professional use.
This masterpiece showcases the strengths of the Micro Four Thirds system, namely its compact size and light weight.
It has evolved from the Mark I to the Mark II and now the Mark III. The Mark III bears the LEICA (LEICA DG) designation, representing the pinnacle of photographic lenses.
Evolution into a LEICA lens
This section outlines the key improvements introduced with the Mark III.
Suppression of Ghosting and Flare
One of the defining features of LEICA DG lenses is their exceptional performance in backlit conditions.
The Mark I and Mark II lenses feature specialised coatings that suppress ghosting. The Mark III goes even further, preventing flare from spreading across the entire frame when a strong light source is present, improving the overall sense of clarity in the image.
To bear the LEICA name, strict standards must be met.
During discussions with LEICA, the issue of flare compromising clarity was raised. With the original lens structure, increasing precision alone would not have been enough to reach the required standard.
By adding new mechanical components, flare was successfully suppressed and image clarity enhanced, enabling the lens to obtain LEICA’s rigorous approval.
Although the optimal solution was structurally simple, reaching that point required an immense amount of trial and error. During the verification process, we repeatedly disassembled the lens, applied sheets to various locations inside, coated parts in black, altered shapes by scraping material away, and then reassembled the lens to check the effect. This process was repeated countless times until we reached the optimal solution. This kind of work is essential to creating a high-quality photographic lens and is a crucial part of our design team’s development process.
Skyscrapers in Osaka
GH6, LEICA DG 12–35 mm F2.8, 12 mm, 1/500 sec, F5.6, ISO 100
Enhanced Colour Reproduction
To achieve both a compact, lightweight design and superior optical performance, this lens employs ultra-high refractive index (UHR) glass with a refractive index close to 2.0.
In general, as the refractive index increases, the transmittance of blue light tends to decrease. This is because the glass composition uses materials that absorb blue light to achieve a high refractive index.
However, thanks to recent research efforts by glass manufacturers, this issue is gradually improving. For the Mark III, we adopted the latest materials, which allow greater transmission of blue wavelengths even at high refractive indices.
For example, many people often photograph buildings against a clear blue sky. In such scenes, the Mark III lens faithfully captures the natural colour of the sky without relying on image processing.
These refinements may be subtle and delicate, but they represent important progress. LUMIX steadily incorporates such technological advancements into its design and development, ensuring continuous improvement of its lenses.
Umeda Sky Building
GH6, LEICA DG 12–35 mm F2.8, 12 mm, 1/1250 sec, F2.8, ISO 100
Reduced Minimum Focusing Distance
Despite its compact and lightweight design, this lens has been developed to enable photographers of all levels, from hobbyists to professionals, to shoot comfortably in a variety of settings. One of the key features in this regard is the minimum focusing distance.
Both the Mark I and Mark II lenses offer a minimum focusing distance of 25 cm across their entire zoom range. We initially believed that this uniformity would make them easier to handle.
However, close-up photography, which allows you to experience the beauty of bokeh, is arguably one of the greatest pleasures of using a mirrorless interchangeable-lens camera. For the Mark III, we therefore revised the design to allow photographers to move even closer to their subjects.
We also revamped the control system to enable focusing as close as 15 cm at the wide-angle end. This gives the lens a maximum magnification of 0.42x, enabling macro-like photography.
Umeda Sky Building, Christmas Market
GH6, LEICA DG 12–35 mm F2.8, 12 mm, 1/80 sec, F2.8, ISO 100
Umeda Sky Building, Christmas Market
GH6, LEICA DG 12–35 mm F2.8, 12 mm, 1/60 sec, F2.8, ISO 125
Optical Design
Now, let's turn to the optical design of the lens, going back as far as the Mark I.
This lens features a five-element optical zoom and an inner focusing system. Its premium design incorporates four aspherical lenses, one Ultra High Refractive Index (UHR) lens, and one Ultra Extra Low Dispersion (UED) lens, all of which are meticulously crafted.
Compact and Lightweight Design
Standard lenses in the Big Three zoom category typically have a large front element that also moves significantly during zooming. This results in a larger structural footprint.
While many previous designs employed a three-element first group, this lens has a two-element configuration. As a result, the spherical aberration that was previously corrected within the first group can no longer be fully compensated for there alone. Instead, the corrective role has been balanced across the second and third groups.
To achieve this, the second and third groups make extensive use of aspherical lenses and special glass materials.
Reducing the thickness of the large first group has also enabled a smaller diameter. Consequently, despite being one of the standard Big Three F2.8 zoom lenses, this lens has a filter diameter of just 58 mm.
Video Recording Performance (Suppression of Lens Breathing)
The Micro Four Thirds system is also ideal for video recording, and this lens has been carefully designed to ensure stress-free performance when filming.
Particular attention has been given to the focusing element in the fourth group. Here, a single element is responsible for the entire focusing function. This allows focusing to be driven by a small motor.
A smaller motor not only contributes to the overall compact and lightweight design, but also operates more quietly and delivers faster focusing speeds. In other words, focusing is smooth, silent, and stress-free.
To achieve this, the element is positioned to suppress changes in image magnification during focusing. Here lies one of the key points of the optical design. The following are some of our design philosophies.
The third group plays a significant role in driving zoom magnification. This group has a strong positive power, and zooming is achieved by driving this high-power group. Because of its substantial positive power, when this group moves, light rays are guided toward the focal point. The lenses in the fourth group, by contrast, are negative power elements that guide these rays away from the focal point in a diverging direction.
In other words, the rays bent inwards by the third group are pushed back outwards by the fourth group. When the lens is zoomed, both groups move together to correct aberrations that occur during zooming. The fourth group plays a key role in compensating for aberrations generated by the third group and is positioned so as to minimise changes in image magnification during focusing.
Focusing is achieved by moving the fourth group to compensate for the shift in the focal plane caused by changes in shooting distance. This alters the angle of the light rays emerging from the third group and causes a change in image magnification.
However, by carefully designing the fourth group, which acts as the focusing group, we have been able to keep this variation to a minimum.
These are the kinds of considerations that guide our optical design process. As a result, we succeeded in developing a zoom lens with focusing performance that is particularly well suited to video recording.
Lastly
Turning to the exterior, while it is only a minor change, the use of the LEICA font enhances its premium feel.
Left: Mark II
Right: Mark III
The '12–35' engraving on the Mark III now features LEICA-branded orange lettering in a new font.
The body colour has also been updated to LEICA specifications.
These refinements will enhance the pleasure of owning this lens.
The optical performance of the LEICA DG lens fully lives up to its distinguished appearance, and we are proud to have brought it to market. It is a lens we can highly recommend.
Photos Taken by the Author
We would like to thank the Osaka Umeda Sky Building for their kind cooperation in allowing us to take these photographs. The view of the magic hour at dusk from the observatory was breathtaking, as was the scene during the day. There was also a bustling Christmas market on the ground floor, full of visitors.
The magic hour as seen from Umeda Sky Building
GH6, LEICA DG 12–35 mm F2.8, 12 mm, 1/60 sec, F2.8, ISO 2500
The magic hour as seen from Umeda Sky Building
GH6, LEICA DG 12–35 mm F2.8, 30 mm, 1/30 sec, F2.8, ISO 3200
Christmas tree under Umeda Sky Building
GH6, LEICA DG 12–35 mm F2.8, 35 mm, 1/30 sec, F2.8, ISO 3200