When Canon developed the groundbreaking full-frame mirrorless EOS R System, the impetus was simple: "redefining optical excellence". The goal was not just to build a new generation of camera, but to make possible a new standard of lenses.
Turning that vision into reality, the Canon RF 70-200mm F2.8L IS USM lens completes the f/2.8 trinity of RF zooms – three fast-aperture, high-performance RF lenses covering ultra-wide, standard and telephoto zoom ranges, providing for practically all professional assignments, from landscapes, portraits and sports, to interiors, fashion and cityscapes.
But the Canon RF 70-200mm F2.8L IS USM is not just an RF-mount equivalent of its venerable EF counterpart – the Canon EF 70-200mm f/2.8L IS III USM. It is significantly shorter and lighter, perfectly complementing the compact Canon EOS R body with the world's smallest professional 70-200mm f/2.8 zoom. In addition to outstanding image quality and the legendary L-series build and reliability, it incorporates pioneering technologies and technical innovations for state-of-the-art speed and performance.
Here the developers take us behind the scenes and reveal five innovative things about the new must-have, super-compact, high-speed telephoto RF lens.
One of the key design priorities behind the Canon RF 70-200mm F2.8L IS USM was to produce a pro-quality lens in a compact form – a lighter-weight telephoto zoom ideal for handheld shooting, which professionals could more easily take anywhere, particularly in their carry-on luggage.
Usually, however, "compact size and high image quality have a contradictory relationship," says Canon Optical Design specialist Kenji Shinohara. So achieving these goals required an innovative, completely new optical design.
"The refractive power of the lenses was increased to maximise the ability of each lens and shorten the overall length," Mr Shinohara explains. "Of course this also affects image quality, so we proactively incorporated new glass materials such as Super UD lenses and UD aspherical lenses for chromatic aberration and spherical aberration correction."
Normally, multiple lenses are required to correct aberrations, and reducing the number of lenses in this way brings significant weight savings.
That's not all. In the EF family of lenses, the zoom mechanism includes a mechanical cam, which controls a lens group. In the Canon RF 70-200mm F2.8L IS USM, this mechanical cam is replaced with a much lighter USM electronic cam.
What's more, the development team achieved new standards of miniaturisation. As Mechanical Design specialist Kazuharu Osawa explains, "the Nano USM is an ultrasonic motor that is not only super compact, but also possesses high torque and is capable of high-speed AF for still images and smooth, silent AF for shooting movies. A new, dramatically smaller Nano USM unit was first included on the Canon RF 24-105mm F4 L IS USM lens, and further modifications have been made on this model for telephoto zoom operation.
"The lens groups on telephoto lenses move a lot, making Nano USM design more difficult," Mr Osawa continues. "For this lens, we succeeded in developing a Nano USM that can deal with the long stroke while maintaining a small size and AF performance. This is expected to be applied on future RF lenses and super telephoto lenses."
Other design innovations were made possible by the technical advantages of the RF mount. "The IS lock mechanism was removed to make the lens lighter," says Development Leader and Mechanical Design specialist Toshihiro Okuda. "On EF mount lenses, a lock ring is required to keep the heavy IS lens group in place when not receiving power. With an RF mount, however, the lens always receives power while it is attached to the camera, eliminating the need for a mechanical lock."
The RF mount's wide throat and short back focus distance, with no need to leave space for a mirror to flip up, meant the overall length of the lens could be significantly reduced. To make the most of this advantage, the design team took the decision early on to use a variable overall length design instead of the more conventional inner zoom construction of the Canon EF 70-200mm f/2.8L IS III USM.
The end result is that the Canon RF 70-200mm F2.8L IS USM lens is just 146mm in length at its shortest and weighs approximately 1,070g, making it more than 50mm shorter and almost one-third lighter than its EF predecessor.
The Canon RF 70-200mm F2.8L IS USM is the first Canon lens to use electronic floating focus control with two Nano USM units. Independent operation of the focusing lens group and floating lens group reduces the minimum focusing distance for improved close-up shooting and delivers further AF precision improvements.
Optical Design specialist Mr Shinohara explains: "The two Nano USM units provide independent control over the focusing lens and floating lens. The electronic floating focus control, a Canon first, improves close-up image quality and shortens the minimum focusing distance to just 0.7m, as compared to 1.2m for the Canon EF 70-200mm f/2.8L IS III USM. The maximum magnification is approximately 0.23x, which is notably higher than on the EF lens.
"Floating focus was originally used on the Canon EF 100-400mm f/4.5-5.6L IS II USM and Canon EF 100mm f/2.8L Macro IS USM lenses," Mr Shinohara adds. "However, these used a comparatively simple mechanical cam. The Canon RF 70-200mm F2.8L IS USM uses an electronic cam to independently operate the two lens groups for high-speed, high-precision still image AF and improved image quality at close distances."
Electrical Design specialist Satoshi Maruyama notes: "This was also the first time an electronic cam system was used for lens group control during zooming on an F2.8L series zoom lens. This lens employs a system that predicts user zoom control for smooth lens movement. This delivers quick control sensations that are not inferior to mechanical cams."
The lens also features a high-precision electronic focusing ring, which does not connect directly to the mechanical mechanism but converts ring rotation into an electronic signal. This optimises responsiveness for still images, delivering exceptional smoothness and speed of focus. Cleverly, it incorporates different parameters for still images and movies, because both smoothness and silence are critical when recording movies.
To achieve the mission of making the lens smaller, the developers also miniaturised the two IS units in the Canon RF 70-200mm F2.8L IS USM. "The IS unit is a new design based on the proven track record of the IS unit from the EF lens series, and technology developed on super telephoto and L-series lenses has been incorporated for further durability," says Mr Okuda.
Combined with the RF mount's faster, higher-bandwidth communication between the lens and camera, image stabilisation is dramatically improved. "The gyro sensor in the lens detects shaking for still images, and information from camera CMOS sensor images is used to detect and correct low-frequency camera shake," such as that caused by your heartbeat or breathing, Mr Maruyama explains.
The Dual Sensing IS system carries out a comparative analysis of these two sets of data, enabling a fantastic five stops of IS for still images (at a focal length of 200mm, CIPA standard compliant). This compares to 3.5-stops of IS on the EF predecessor. For movies, Combination IS uses in-lens optical IS and in-camera 5-axis electronic IS.
In addition to Canon's well-known, proven Image Stabilizer modes – Mode 1, for still subjects, which can handle any kind of shaking, and Mode 2, for panning shots of moving subjects – this lens includes the additional Mode 3.
"This is for shooting subjects that move unpredictably," says Mr Maruyama. "This mode continuously calculates the amount of camera shake and operates only during the exposure, not while the photographer is checking the composition. Some pros mentioned that the image in the viewfinder feels unnatural due to rebound when the camera is moved while IS continues operating. Mode 3 is recommended for such users."
Product Planning specialist Kaishi Kawai adds: "Because this product is extremely compact and has a bright f/2.8 aperture and IS, it's a good lens for indoor sports. Mode 3 is a good choice for such scenes. There is a lot of intense movement in sports such as basketball, so Mode 3 enables shooting without rebound in the viewfinder."
"This lens is designed for reliability and durability that is equal to or surpasses the Canon EF 70-200mm f/2.8L IS III USM," Mr Okuda says. "It also has the same level of shock resistance as other L-series lenses, and technology that prevents changes to optical performance due to long-term usage.
"Some photographers who use a variable overall length lens have reported that the lens barrel is inadvertently extended when they point the camera downward," he adds, simply because of the effects of gravity. Thanks to the RF mount, the lens always receives power when connected to the camera, enabling the designers to solve this issue.
"Developing a variable overall length zoom lens poses structural challenges in keeping out dust," Mr Okuda continues. "Pressure is generated when extending the lens from the wide to tele front group, sucking in air. We designed the ventilation route of the lens so that air would not be sucked in from any unexpected locations, ensuring that air flow is exactly as designed." Dust and water resistant sealing is applied to all lens joints and switch panels.
Mr Kawai adds that the front and rear surfaces of the Canon RF 70-200mm F2.8L IS USM lens have a fluorine coating, which repels oil and moisture, helping prevent smudging. Dust and droplets of water can be wiped off with just a dry cloth.