On 24 October 2019, Canon announced the RF70-200mm f/2.8L IS USM, completing the RF mount f/2.8 zoom lens trinity. Designed to provide high image quality within a compact, lightweight body, the lens, whose telephoto zoom range completes the EOS R system, incorporates a number of new features. What is this lens about and how was it achieved? Find out in this article, where we have included some interesting revelations from the lens developers.

1. Compact, light, portable: Words seldom used to describe a fast professional-grade telephoto lens,but... 
2. The Nano USM on this lens is a little different
3. A new Canon first: Dual Nano USM-driven electronic floating focus control system
4. Fewer lens elements, but better optical performance
5. What’s with that third IS mode?
6. The bundled white lens hood is the ultimate status symbol

EOS R/ RF70-200mm f/2.8L IS USM/ FL: 200mm/ Aperture-priority AE (f/2.8, 1/160 sec)/ ISO 100/ WB: 4800K

 

1. It’s a fast professional-grade telephoto zoom lens that is also lightweight and compact

Tasked with developing a telephoto zoom lens for the RF mount, the Canon lens developers had two goals in mind:

i) To ensure high image quality that took full advantage of the benefits of the RF mount
ii) To make the lens smaller and lighter, hence retaining the portability and mobility of a mirrorless camera system

With this, they hoped to cater to the needs of photographers who treasured their fast, professional-quality telephoto zoom lens but also desired better mobility.

Toshihiro Okuda (Development Leader/Mechanical Design): Although the EF70-200mm f/2.8L IS III USM received high praise for its image quality, it requires a large camera bag when shooting overseas and deep in backcountry locations, making it difficult for some to carry.

Kaishi Kawai (Product Planning): With this in mind, we set our sights on creating a shortened overall length that could easily fit in a small camera bag. 

Their efforts succeeded: Weighing a relatively lightweight 1070g, the RF70-200mm f/2.8L IS USM is up to 53mm shorter than the EF70-200mm f/2.8L IS III USM when fully retracted. This makes it easier to store in a camera bag and carry around, even as hand-carry luggage on a plane, providing portability that is true to the EOS R system.

An extendable design that is dust-proof and water resistant
This lens extends in size when you zoom in, and retracts when you zoom out.

Some users might be concerned that this extendable design makes the lens more prone to dust and moisture infiltration, as air will be sucked in when zooming in. However, the RF70-200mm f/2.8L IS USM is designed with an air ventilation route that controls air flow and prevents air from being sucked in from unexpected places. This route incorporates dust-resistant material, as well as material that allows air to pass through but not moisture, which ensures that the lens remains dust and water resistant.

 

2. Nano USM: The key to a smaller, lighter body

It took a huge breakthrough to produce a lens that could perform at least on par with the EF70-200mm f/2.8L IS III USM within a smaller, lighter body. That breakthrough came in the form of an electronic floating focus control system driven by two Nano USMs (ultrasonic motors).

Okuda: Part of the zoom mechanism from the EF70-200mm f/2.8L IS III USM consisting of a mechanical cam (mechanical lens group control) was replaced with a Nano USM-driven electronic cam. This eliminated the need for mechanical cam components, contributing to a more lightweight design.

EOS R/ RF70-200mm f/2.8L IS USM/ FL: 108mm/ Manual exposure (f/2.8, 1/200 sec)/ ISO 200/ WB: Flash

A tiny motor barely the size of a fingernail, the Nano USM possesses very high torque, and is capable of not only high-speed AF during still shooting, but also smooth, quiet AF ideal for shooting video.

Find out more about Nano USM in:
Nano USM: Fast and Smooth Focusing At Your Fingertips 

One of the key challenges that the developers faced was to modify the Nano USM for telephoto zoom operation. This was not the first time Nano USM was modified: The RF24-105mm f/4L IS USM , the first L lens to use the Nano USM, uses a Nano USM unit that was drastically smaller than previous Nano USMs.

Kazuharu Osawa (Mechanical Design): The lens groups on telephoto lenses move a lot (have a large stroke), making Nano USM design more difficult. For the RF70-200mm f/2.8L IS USM, we succeeded in developing a Nano USM that can deal with the long stroke while maintaining a small size and AF performance.

 

3. The new electronic floating focus control system makes it possible to shoot closer with higher image quality

The resulting dual Nano USM floating focus system, which is included for the first time on a Canon lens, makes it possible to drive the two lens groups that not only make it possible to retain lens performance within a smaller, lighter body, it also makes it possible to shoot subjects from a physically closer distance, with a larger maximum image magnification and better close-up image quality.

Kenji Shinohara (Optical Design): Using two Nano USM units enables us greater freedom over lens group placement, which links to high image quality. The two Nano USM units provide independent control over the focusing lens and floating lens. The electronic floating focus control, which drives the floating lens electronically, is a Canon first.

The use of two Nano USMs to drive the lens groups individually enables a high degree of quietness, power-efficiency and speed within a smaller, lighter body. It also makes it possible to shoot subjects from a physically closer distance, with a larger maximum image magnification and better close-up image quality.

 

 

EOS R/ RF70-200mm f/2.8L IS USM/ FL: 200mm/ Manual exposure (f/2.8, 1/10 sec)/ ISO 100/ WB: 5200K

The electronic floating focus control system reduces the closest focusing distance to as close as 0.7m away, and enables a magnification of up to 0.23x. This lets you achieve a macro-like effect by simply by shooting at the telephoto end from the closest focusing distance.

 

4. It uses 6 special lens elements, but has fewer lens elements overall compared to its EF counterpart

The RF70-200mm f/2.8L IS USM consists 17 lens elements in 13 groups, which is one reason why it is lighter than the EF70-200mm f/2.8L IS III USM which has 23 elements in 19 groups. However, optical performance has in fact improved.

Shinohara: We had to modify Canon development optical design tools to maximise the potential of electronic floating focus control.

The lens includes one Super UD lens, three UD lenses, one UD aspherical lens, and one glass-molded aspherical lens. The glass-moulded aspherical lens closest to the image plane is treated with special Subwavelength Structure Coating (SWC) to reduce flaring and ghosting. The short back focus distance on the RF mount enables large lens elements to be placed closer to the image sensor, and this allows SWC to suppress glaring more effectively.

Lens construction

A: Aspherical lens elements
B: UD lens elements
C: UD aspherical lens elements
D: SWC
Smudge-resistant fluorine coating on the front and rear lens surfaces

 

5. Just like super telephoto EF lenses, it has IS Mode 3

The image stabilisation (IS) performance of this lens will probably be an important consideration, especially for use in sports scenes. Existing lenses in the same class come with two IS modes, but the RF70-200mm f/2.8L IS USM comes with three.

Satoshi Maruyama (Electrical Design): MODE 1 is used for still subjects, and can handle any kind of shaking. MODE 2 is for panning shots of moving subjects. MODE 3 is for shooting subjects that move unpredictably. These modes continuously calculate the amount of camera shake and only operate during the exposure, not while the photographer is checking the composition. Some professional photographers 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.

 

EOS R/ RF70-200mm f/2.8L IS USM/ FL: 70mm/ Manual exposure (f/8, 0.4 sec)/ ISO 200/ WB: Auto

The lens supports up to five shutter speed stops’ equivalent of image stabilisation, and is compatible with Dual Sensing IS. During movie shooting, it also supports Combination IS, which combines the optical in-lens IS system with the five-axis in-camera digital IS system to ensure stable, seamless footage.

Also see:
Lens FAQ #3: How are Image Stabilisation Stops Determined? 

 

6. It comes with a white lens hood—the ultimate status symbol for a Canon lens

 

The RF70-200mm f/2.8L IS USM inherits the distinctive white colour of Canon’s beloved white EF telephoto lenses for a good reason: The white is due to the heat shield coating, which prevents the lens barrel from overheating even under the hot sun. In addition, it comes with a white lens hood, previously included only with top-end professional lenses such as the super telephoto prime lenses.

The white colour is not the only thing that this lens has inherited, of course—it also incorporates Canon’s existing technologies and know-how alongside new innovations. You can’t expect less from a lens that is not just poised to be one of the EOS R system’s core lenses, but also part of Canon’s new Holy Zoom Trinity.

 

RF70-200mm f/2.8L IS USM

 

Lens hood ET-83F (W III)

 

Click here to download and read the full interview with the developers (PDF)

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Find out more about RF lens technology and the other RF lenses in:
In Focus: RF Lenses

Trying to decide whether to buy the EOS R or EOS RP? Check out:
EOS R vs EOS RP: Which to Choose?

 

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