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Seeing is believing: how Canon created the EOS R System

For the last three decades, Canon engineers have been on a journey to create lenses and cameras that behave as closely to the human eye as possible. With the EOS system they got closer than anyone in realising this goal, and now with the EOS R System, they are closer still. This is the story of their tireless dedication to achieving what many never thought possible.

Looking back to those pre-digital days of 1987 it’s easy to forget the huge impact the EOS system had on the world of photography. Fast and reliable autofocus lenses plus a camera body that offered intuitive, comfortable handling? Surely the stuff of dreams. But Canon made it a reality and revolutionised camera performance in the process.

Canon EOS R with RF 24-105mm lens
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An opportunity to reinvent

Over the course of the last 30 years the company has evolved the EOS system by introducing pioneering and ground-breaking technologies to help photographers and filmmakers achieve their creative vision. But time stands still for no man, and with the evolution of mirrorless cameras – with many professionals choosing them as second bodies to complement their existing DSLR system – Canon recognised a fundamental shift in the market.

“Even though times have changed dramatically, such as digitisation, increasing pixel counts of cameras, and support for movies, the EOS system is far from becoming obsolete, and we are leading the world of still images and movies today. Our goal was to create an image input system that would continue to develop over the next 30 years,” comments Canon engineer Manabu Kato, Deputy Senior General Manager of the ICB Optical Products Development Centre at Canon Inc.

Manabu Kato
“We began by re-examining the strengths of the EOS system. The answer was the EF mount. Its true meaning lies in achieving an image input system with a new form, in which the camera and lens demonstrate high performance working together.” - Manabu Kato

He continues: “We did not set out to create a small, lightweight camera. The ideal lens was what Canon was strived for. This new mount, and the 35mm full-frame mirrorless structure, were the best solution to achieving our ideals.”

Testing and developing an all-new lens mount

Fundamental to the success of this new system was the RF lens mount. It was crucial to reimagine the EF mount for the future and this is where the design team faced their biggest – and most exciting – challenge. To design a new lens system that took full advantage of the mount and yet still allowed existing EF lenses to be used – vital if the camera is to be used by professionals already invested in Canon equipment.

“All of the past EF lenses work as expected with the latest EOS cameras,” assures Yoichi Sato, Senior Project Manager, ICB Products Development Centre. “This is proof that the EOS communication system had great expandability and flexibility. With the EOS R System as well, I wanted to achieve a large system potential that would live up to our predecessors’ achievements.”

EOS R aluminium body
EOS R System flange back

Engineers realised that the larger the mount diameter, the shorter the back focus, which meant that optical design possibilities increased. Manabu Kato explains: "By being able to place a lens with a large diameter close to the focal plane, the degree of freedom of optical design is enhanced dramatically. The four lenses developed as the first stage of the RF lenses have realised these advantages.”

Fundamental to the performance of these new lenses is faster transfer of information. A twelve-pin mount was developed to allow lightning fast communication speeds. “The exchange of electronic information between the lens and the camera is expected to increase more and more in the future. In order for the system to continue to develop, the RF mount makes a significant increase in communication speed possible,” reveals Senior Engineer Akihiro Kawanami.

Canon EOS R high speed communication
A simulation of the RF mount data communication system.

Optical and mechanical breakthroughs

The four RF lenses offer unrivalled image quality and performance. “No matter how outstanding the optical design is, it will not make sense unless there is technology to shape it,” advises Seichi Kashiwaba, General Manager of the ICB Optical Products Development Centre at Canon Inc. “The RF lens is the crystallisation of a new effort not only in optical but also in mechanical design.”

These four L-series lenses carry the RF prefix in recognition of the EOS R System and consist of an RF 35mm f/1.8 Macro IS STM, RF 24-105mm f/4L IS USM zoom, RF 28-70mm f/2L USM, and an RF 50mm f/1.2L USM prime.

Seichi Kashiwaba holding RF lens
“Attempting something new. That is the source of innovation in design and production technology. It is also Canon's strength which can be dealt with consistently from optical design to mechanical design and production." - Seichi Kashiwaba

“When I saw the RF 50mm f/1.2L USM and the RF 28-70mm f/2L USM for the first time, I thought ‘These are lenses that really make me feel like shooting photos.’” smiled Naoya Kaneda, Group Executive of the ICB Optical Business Group. “Since the EF lenses also have large aperture lenses of the same brightness, I thought I knew what to expect in terms of the depth of field. However, when looking through the electronic viewfinder, the depth of field was shallower, and the background blur effects were richer than I had expected. 

What matters to professionals and advanced amateurs is that you can express yourself as you imagine, and that you can obtain final results that differ from other people’s. In fact, I have been involved in the development of the EOS system for a long time, and the fact that a system capable of this is right in front of us fills my heart with pride.”

Canon RF lens range

Unique and ground-breaking designs

The RF lenses differ from EF lenses in that they have been designed from the ground up for the new full-frame mirrorless Canon EOS R body. They offer higher levels of image quality thanks to the nature of the larger mount and flange back design, while processing speeds have also been significantly raised.

Increasing the communication speed was instrumental in offering a higher level of overall camera and lens performance. With the EOS R System, in addition to the optical information, the lens also holds optical correction data. This includes the Digital Lens Optimizer, which was previously stored in the camera’s memory.

“The faster the communication speed, the more possible it is to send this data to the camera in a shorter time,” explains Senior Engineer Akihiro Kawanami. “In other words, the system can start up even faster after replacing the lens. In addition, it is possible to improve various functions such as image stabilization by coordinating the lenses and camera.”

The Image Stabilization in the Canon RF 35mm F1.8 MACRO IS STM
The Image Stabilization in the Canon RF 35mm f/1.8 Macro IS STM (simulated).

One of the major optical breakthroughs made with the RF lenses is the newly developed focus group retention mechanism. As the diameter of the lenses increases and the image quality improves, the focus group becomes heavier, and the load at the time of focusing tends to increase. Moving the heavy focus group smoothly with a small amount of force was key to high performance, and maintaining stability.

The EOS R has been developed for movies as well as stills, so the inclusion of a 24-105mm lens with Canon's special Nano USM motor was important for the new lens line-up.

“I wanted to use Nano USM for the lens actuator,” explains lead engineer Katsuhiro Inoue. “It is compact, but has a lot of power. It is also extremely controllable and quiet, making it ideal for shooting movies.

Canon Dual pixel CMOS AF and Nano USM
Canon RF 24-105mm f/4L IS USM: Dual Pixel CMOS AF + Nano USM (simulated).

“However, there was one problem,” he continues. “For commonly used lenses only, we want to miniaturise as much as possible considering handling ability, but even with existing Nano USMs, the unit is too thick. To make it slimmer, through repeated trial and error the designers tried to reduce the thickness of the lens barrel and mechanical structure as much as possible. How much can the outer diameter be slimmed, and how neat can the form be? The Nano USM has important keys to making it slimmer.

Nano USM on finger
The new Nano USM fits within a small space of the focus unit, which contributes to making the Canon RF 24-105mm f/4L IS USM slimmer. Such technological innovations accelerate Canon's lens development further.
Old and new Nano USM
Left: Conventional-type Nano USM
Right: New Nano USM

“Nano USM transfers the vibrations generated by the piezoelectric ceramic element to the slider via a chip-shaped metal elastic body. The metal elastic body is thin and small enough to rest on your fingertip.”

A system for the next 30 years

Final word on the birth of this new EOS system must goes to ICB Products Group Group Executive, Yoshiyuki Mizoguchi: “As the first products of the EOS R System, we will introduce the EOS R camera and four RF lenses with specs that did not exist before. Specs that did not exist before means that you can create images that could not be captured before. This also means that the range of activities of the camera will be expanded, which should essentially contribute to expanding the range of shooting. That is the value that Canon strives to offer, and the reason for establishing a new system.

Canon EOS R range

“I am proud to say that we were able to get that message across clearly with this camera and the series of lenses. However, that is not the goal of the EOS R System development project. It should continue to be developed for years, and decades from now. Canon has a mission to contribute not only to people with photography as a hobby, but also to more industry specialists. 

With the EOS R System and RF lens, it can support even higher resolution CMOS sensors and various applications. As an example, large drones are required for 8K aerial photography, but they could also be made smaller. As a consumer product, and as a commercial equipment, it has great potential.”

Written by David Corfield


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