The inspiration behind Canon’s RF 600mm F11 and 800mm F11 super-tele lenses

In July, Canon announced a pair of super-telephoto fixed-aperture lenses for its RF lens mount. The new RF 600mm F11 IS STM and RF 800mm F11 IS STM lenses are distinct among Canon’s modern offerings but are reminiscent in design and philosophy to some of Canon’s R lenses from 1960.

Six decades ago, Canon released the R300mm F4, R400mm F5.6, R600mm F5.6, R800mm F8 and R1000mm F11 super-telephoto lenses. While not fixed aperture lenses like the new RF lenses, the vintage bellows-driven lenses were nonetheless the inspiration for this year’s modern interpretations. In a Japanese-language interview published by DC Watch, Canon’s Chief of Lens Product Planning, Kengo Iezuka, notes that the EOS R system allows him and his team to create new user experiences for modern photographers. This includes breaking down ‘the three barriers of super-telephoto lenses,’ which he states are weight, size and cost. In 1960, Canon worked to overcome these challenges with its R lenses, and Iezuka believes Canon’s RF 600mm F11 and RF 800mm F11 lenses do the same in 2020.

Canon R600mm f/5.6 lens. The lens was first marketed in January 1960. Image credit: Canon, Canon Camera Museum

When Iezuka was a child and wanted to capture wildlife images of a Little Egret, he was unable to due to the expense of super-telephoto lenses. Iezuka says via translation, ‘I knew that there were many people who gave up what they wanted to shoot and the expressions they wanted to shoot because they couldn’t buy a super-telephoto lens and couldn’t carry it because it was big and heavy. With the EOS R system, I think I was finally able to get closer to the dream super-telephoto world. I would like you to enjoy shooting things that you couldn’t shoot before and the expressions you wanted to shoot with this 600mm/800mm F11 lens.’

In elaborating further upon how the Canon EOS R system allows the three barriers of super-telephoto lenses, Iezuka states that Canon’s Dual-Pixel CMOS AF allows for strong autofocus performance even in low light, or when using a lens with a smaller maximum aperture, such as F11. In 1960, the sensitivity of film was stricter, requiring faster apertures in the case of the R400mm F4.5, R600mm F5.6 and R800mm F8. However, today, Canon’s EOS R system allows for much more flexibility when designing new lenses. In fact, the EOS R can even work with F22, allowing Iezuka and his team to utilize an F11 design that can incorporate a 2x teleconverter.

If Canon had pursued an F8 aperture, the lens would have been larger and heavier. An F16 lens would have worked without a teleconverter, but not with a 2x TC attached. It was around this point in the design process when the team first considered making the lens with a fixed aperture. Ultimately, removing the aperture unit allowed for reduction in weight and cost, both critical design goals for Iezuka and the team at Canon.

Iezuka also shared that the RF 600mm and 800mm lenses were not his first attempt to create a lightweight and cost-effective super-telephoto lens. He had previously explored the idea for SLR cameras. ‘I wondered if I could manage to get closer to the world of super-telephoto lenses that exceed 400mm,’ Iezuka said, ‘I considered increasing the F-number as I did this time, but it didn’t work. If you increase the F value, you can only autofocus at the center of the [frame]…so I gave up.’ The new RF lenses offer autofocus coverage of 60% x 40% (W x H) with the recent Canon EOS R5 and R6 full-frame mirrorless cameras.

Iezuka also considered zoom lenses, but this design would increase the weight too much to be able to carry the lens around all day. The RF 600mm lens weighs approximately 2.05lb and the RF 800mm weighs about 2.78lb. In order to maintain a lightweight design and ensure the lenses are affordable, metal parts are kept to a minimum and much of the lens is constructed using resin. In order to utilize a collapsible design, many parts had to be molded, which is unique for Canon’s lenses. The collapsible design came from one of the youngest members of the team, Iezuka says, and was the result of internal competition within the department.

There is much more excellent insight into the design process in the full interview, so be sure to check that out. Click the following links for more information on the Canon RF 600mm F11 IS STM and RF 800mm F11 IS STM lenses.

(Via PetaPixel)