Canon RF 15-35mm F2.8L IS USM Review

The Canon RF 15-35mm f/2.8L IS USM is a wide-angle zoom lens designed specifically for use on Canon’s RF-mount mirrorless full-frame cameras such as the Canon EOS R5 and R6. In fact, it’s currently the widest optic that the manufacturer offers with the RF mount.

As one of Canon’s ‘L’ lenses, the RF 15-35mm f/2.8L IS USM is aimed at professional and experienced enthusiast photographers. Its focal length range makes it of interest to landscape and architecture photographers and those wishing to shoot within cramped interiors.

As an L-series lens, the Canon RF 15-35mm f/2.8L IS USM is weather-sealed and both the front and rear element have fluorine coatings to repel dust and water droplets.

Inside the barrel, 16 elements are arranged in 12 groups. These include three aspherical elements to compensate for wide-angle distortion and spherical aberration, and two UD (ultra-low dispersion) elements for enhanced sharpness across the image.

In addition, some elements have Subwavelength Structure Coating (SWC) and Air Sphere Coating (ASC) to reduce flare and ghosting.

Focusing is handled by the Nano USM (ultrasonic motor) system. This technology was first unveiled in 2016 and it combines the speed of ring-type USM with the smooth quietness of an STM (stepping motor) system.

Although Canon’s latest mirrorless cameras have in-body image stabilisation, the RF 15-35mm f/2.8L IS USM has image stabilisation built-in. This is claimed to enable the shutter speed to be reduced by as much as 5EV when the camera and lens are hand-held.

The maximum aperture is a constant f/2.8 throughout the focal length range, which means the exposure doesn’t change when zooming from one focal length to another.

Although mirrorless cameras tend to be smaller than comparable DSLRs, the lenses still need to cover a full-frame sensor, which means they can be pretty beefy. And naturally, a 15-35mm full-frame lens with a constant aperture of f/2.8 is unlikely to be small.

At 88.5 x 126.8mm and  840g in weight, the Canon RF 15-35mm f/2.8L IS USM is pretty hefty but despite its wider focal length range, the Canon RF 15-35mm f/2.8L IS USM is a smidge smaller than its closest match with the Canon EF mount, the EF 16-35mm f/2.8L III USM.

I shot with the RF 15-35mm f/2.8L IS USM on the Canon R5 and R6, which both have a good deep grip and they felt secure in my hand.

The RF 15-35mm f/2.8L IS USM’s broad zoom ring has a step-up in size roughly at its mid-point, which makes it easy to identify and differentiate from the manual focus ring that is further forward. Both have a smooth, easy action.

At the far end, close to the front element, the Canon RF 15-35mm f/2.8L IS USM has a dedicated control ring. This can be customised via the camera’s menu to control one of a wide selection of features including the AF method, exposure compensation, aperture, shutter speed and ISO. I used it for adjusting the exposure compensation.

One disappointment with the Canon RF 15-35mm f/2.8L IS USM is that the control ring doesn’t have a ‘de-click’ control. The clicks are handy for photographers, but depending on the location of the mic, they’re audible in video. Canon has a paid de-click service for its RF lenses, but it would be preferable to be able to switch the clicks on and off as you like.

As soon as I held the camera to my eye with the Canon RF 15-35mm f/2.8L IS USM mounted, I was impressed by the lack of curvilinear distortion. Even at 15mm straight lines hardly seem to diverge from their true path. The little distortion that is present can be corrected in-camera using the Peripheral illumination correction feature within the ‘Lens aberration correction’ section of the camera’s menu, or using the profile available in Adobe Camera Raw and Lightroom etc.

Checking images from the 45Mp Canon EOS R5 at 100% on a computer screen reveals that the Canon RF 15-35mm f/2.8L IS USM captures an excellent level of detail at the centre of the frame at all aperture settings. At the 15mm end, there’s a noticeable drop-off in sharpness towards the corners, but it’s not dramatic.

There’s a slight drop-off towards the corners at other focal lengths as well, but even at 100% on-screen, it’s less apparent than at 15mm. Closing down from f/2.8 to f/4 sharpens up the detail across the board, but most noticeably at 15mm.

Sharpness levels are maintained well as the aperture is closed down but by f/16 there’s very slight softening as a result of diffraction and by f/22 it’s more evident when images are examined at 100%. It’s subtle, but it’s worth looking at the depth of field and hyperfocal distance tables to ensure you only close the aperture by as much as you need.  For instance, at 15mm and f/8, focusing at the hyperfocal distance of 0.95m gives depth of field that extends from 0.49m to infinity. And actually, of the marked focal lengths (15, 20, 24, 28 and 35mm) 35mm is the only point at which you need to close the aperture to f/22 to get the focus to extend to infinity when using hyperfocal distance focusing. At 35mm at f/22, the hyperfocal distance is 1.84m and the depth of field starts at 0.92m.

So in fact, there are few occasions that you actually need to use the smaller aperture settings at the widest end of the lens.

Even without using the lens correction profiles, vignetting isn’t an issue with the RF 15-35mm f/2.8L IS USM. I also spent quite some time hunting through my images looking for chromatic aberration but I haven’t found any.

The Canon R6 and R5 both feature in-body stabilisation with claimed shutter speed compensation of up to 8EV, trumping the 5EV offered by the RF 15-35mm f/2.8L IS USM. With the RF 15-35mm f/2.8L IS USM at 15mm on the Canon R6, I was able to get around 50% of my hand-held images shot at 1sec sharp. That’s a compensation factor of 4EV.

As promised, the RF 15-35mm f/2.8L IS USM focuses quickly and quietly. The focusing is also very smooth and usable during video shooting as well as for stills.

Follow the link to browse and download full-resolution images from the Canon RF 15-35mm f/2.8L IS USM.

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The Canon RF 15-35mm f/2.8L IS USM has a list price that’s enough to bring you out in a cold sweat but it’s also a phenomenally good wide-angle optic that delivers images that have to be seen to be believed. There are no concerns about curvilinear distortion making straight lines bend like bananas and you can forget about vignetting and chromatic aberration. There is a slight drop-off in sharpness towards the corners at the 15mm end and you might want to avoid using the smallest aperture to get the very best from the lens, but it really is very good indeed.