In summary
This is the first – and so far only – ultra-wide lens available for Canon’s EOS-R system and, as such, should be popular with landscape and architectural photographers. Its fast, constant f/2.8 maximum aperture will make it ideal for shooting in low-light interior conditions and for capturing atmospheric outdoor evening shots.
RF 15-35mm f/2.8L IS USM lens has built-in stabilisation and a design that ensures minimal distortion, even when the built-in corrections in Canon’s cameras are not applied (for example when shooting raw files).
Potential applications also include astrophotography and event photography, particularly when taking portraits of large groups of people in cramped locations. It could also be used for close-up street photography.
While relatively large for a wide-angle zoom lens, of its type, this lens is moderately light for such a fast lens, making it a workable partner for the EOS RP camera we used for our tests.
The Nano USM focus system is very fast and quiet enough for video applications, including documentary videos, where the five-stop stabilisation will come in handy when shooting hand-held.
Full review
The RF 15-35mm f/2.8L IS USM lens is the final member in a trio of stabilised, L-series f/2.8 lenses announced by Canon at the end of August in 2019. We reviewed the RF 24-70mm f/2.8L IS USM lens in December 2019 and the RF 70-200mm f/2.8L IS USM lens in January 2020. All three lenses include built-in stabilisation, with up to five stops of shake correction available in the 15-35mm lens. The new RF 15-35mm f/2.8L IS USM lens is similar in size to the equivalent EF mount lens, the EF 16-35mm f/2.8L III USM, which is 50 grams lighter because it lacks stabilisation.
Side view of the RF 15-35mm f/2.8L IS USM lens without end caps or lens hood. (Source: Canon.)
Despite the slightly wider angle of view of the RF lens, the optical designs of the EF and RF lenses are also very similar, with the stabilisation element accounting for the extra element in the RF’s 16 elements in 12 groups design. The optical design remains relatively complex.
Three glass-moulded aspherical elements have been used to reduce overall weight while also controlling spherical aberration, minimising distortion and providing better edge-to-edge sharpness. Two UD (Ultra-low Dispersion) elements are included to decrease chromatic aberrations.
Canon has added its proprietary SWC (Subwavelength Structure Coating) which suppressed unwanted reflections from light entering the lens at high angles of incidence. ASC (Air Sphere Coating) has been added to reduce the occurrence of ghosting and flare. The rounded nine-blade diaphragm produces pleasing bokeh and attractive ‘sun stars’ in strong backlighting.
Fluorine coatings have been applied to the front and rear surfaces of the lens to repel dust, water droplets, grease and dirt. This enables the lens to be kept grime-free by simply wiping it with a clean, lint-free cloth. The lens is supplied with the E-82II lens cap, EW-88F petal-shaped lens hood, end cap and LP-1222 soft carrying pouch.
Angled view of the RF 15-35mm f/2.8L IS USM lens with the supplied EW-88F lens hood fitted. (Source: Canon.)
Who’s it For?
This is the first – and so far only – ultra-wide lens available for Canon’s EOS-R system and, as such, should be popular with landscape and architectural photographers. Its fast, constant f/2.8 maximum aperture will make it ideal for photographers who shoot for real estate agencies, especially when working in low-light interior conditions and for capturing atmospheric outdoor evening shots.
Its most attractive features include built-in stabilisation and a design that ensures minimal distortion, even when the built-in corrections in Canon’s cameras are not applied (for example when shooting raw files). Potential applications also include astrophotography and event photography, particularly when taking portraits of large groups of people in cramped locations. It could also be used for close-up street photography.
While relatively large for a wide-angle zoom lens, of its type, this lens is moderately light for such a fast lens, making it a workable partner for the EOS RP camera we used for our tests. It is eminently suitable for location work with a weatherproof body like the EOS R or up-coming R5 (for which a release date is currently unavailable).
The Nano USM focus system is also very fast and quiet enough for video applications, including documentary videos, where the five-stop stabilisation will come in handy when shooting hand-held.
Build and Ergonomics
Most of the basic structure of this lens is made from magnesium alloy, with an external cladding of high-quality polycarbonate that gives it a smooth appearance. Tight tolerances between moving components and extensive weather-resistant sealing provide a reassuring ‘quality’ feel.
Focusing is totally internal but the inner barrel extends by about 14 mm while zooming from the 35mm to the 15mm position. A 5 mm wide section at the front of inner barrel carries a bayonet mounting for the shallow, petal-shaped lens hood, which can be reversed for transport or storage.
Just behind the red Canon branding ring and approximately 5 mm back from the leading edge of the outer barrel is the programmable control ring. It’s roughly 15 mm wide with a 10 mm wide hatched band that makes it easy to identify by touch.
The control ring can be programmed via C-Fn III-6 in the camera’s Custom menu to adjust one of a range of exposure settings, including aperture, ISO and exposure compensation. By default, it has click stops to enable users to control how much it is being turned. (It can be de-clicked by the Canon Service Centre – for a fee – if silent operation is required.)
A 5 mm wide band separates the control ring from the focusing ring, which is 17 mm wide and almost completely clad with fine ridges to provide a secure grip. Since focusing is driven from the camera, this ring turns through 360 degrees when power is switched off.
The zoom ring is located immediately behind the focusing ring. It’s roughly 40 mm wide with noticeably thicker ridges than the focusing ring and slopes inwards about half way along its length. A 3 mm wide un-ridged band on the trailing edge of the zoom ring is stamped with focal length marks for the 15mm, 20mm, 24mm, 28mm and 35mm settings.
Behind the zoom ring is an un-ridged section of the barrel that is approximately 25 mm wide. Slider switches for the focus mode (AF/MF) and image stabiliser (ON/OFF) are located around the left hand side of this section of the barrel.
The lens barrel then steps in to the metal lens mount, which has a red index mark on its outer surface for mounting the lens plus a rubber ring to keep out moisture and dust. Inside the mount are 12 gold-plated contact points for exchanging signals between the lens and the camera.
Unlike some ultra-wide-angle lenses, this lens has a removable hood so filters can be easily fitted via the 82mm diameter attachment ring. The supplied hood has a locking button to keep it in place, whether it’s positioned for shooting or reversed for storage. It’s easy to attach via the bayonet fitting at the front of the inner barrel.
Performance
Imatest showed the review lens to be a fair performer on the EOS RP camera we used for our tests. However, it only came close to meeting expectations for the sensor’s resolution in JPEG files when sampled around the centre of the frame, where the highest resolution was obtained at the 35mm focal length. With raw files, which were converted in to 16-bit TIFF format with Adobe Camera Raw, resolution comfortably exceeded expectations around the centre of the frame but fell a little short towards the periphery.
The best performance at all focal lengths was between f/3.5 and f/5.6. As expected with such a wide-angle lens, edge softening was found at all focal lengths and noticeable with aperture settings down to about f/11, where diffraction began to take effect. The graph below shows the results of our Imatest tests.
Lateral chromatic aberration remained entirely within the ‘negligible’ band, which is expected since this flaw is normally corrected by default in JPEG files. Interestingly, a similar result was obtained with uncorrected CR3.RAW files, although traces of coloured fringing could be seen along high-contrast edges in uncorrected raw files near the periphery of the image frame. In the graph of our test results below, the red line marks the border between ‘negligible’ and ‘low’ CA.
Because rectilinear distortion and vignetting are corrected by default in JPEG files in EOS cameras, we used CR3.RAW files to measure both aberrations. Barrel distortion was visible at the 15mm focal length but by 20mm it had switched to slight pincushion distortion. Interestingly, this level of distortion didn’t change noticeably at longer focal lengths.
Vignetting could be seen at f/2.8 with all focal lengths, which was expected for this type of lens. It was most obvious at 24mm but largely eliminated by stopping down to between f/4 and f/4.5. As with distortion, this aberration can be easily corrected when converting raw files into editable formats.
Backlit subjects were handled very well, although we found a few flare artefacts when a bright light source was just within or just outside of the frame, especially with wider angles of view. Fortunately, there was no apparent loss of contrast due to veiling flare.
Autofocusing was generally fast and accurate and the built-in stabilisation system worked well for all our test shots. Close focusing is limited to 28 centimetres, which applies throughout the zoom range and provides interesting perspectives at the widest angles of view.
The fast maximum apertures across the zoom range mean that soft backgrounds could be obtained at the widest lens aperture settings even with the 15mm focal length. Low contrast transitions were usually smooth but outlining was often found around bright highlights, especially with the 35mm focal length.
Conclusion
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SPECS
Picture angle: 110 degrees 30 minutes to 63 degrees
Minimum aperture: f/22
Lens construction: 16 elements in 12 groups (including 3 glass-moulded aspherical and 2 UD elements plus SWC, ASC and fluorine coatings)
Lens mounts: Canon RF
Diaphragm Blades: 9 (circular aperture)
Weather resistance: Yes
Focus drive: Nano USM
Stabilisation: Yes, 5 stops
Minimum focus: 28 cm
Maximum magnification: 0.21x
Filter size: 82 mm
Dimensions (Diameter x L): 88.5 x 126.8 mm
Weight: 840 grams
Standard Accessories: E-82 II lens cap, rear end cap, EW-88F lens hood, LP-1222 soft carrying pouch
Distributor: Canon Australia; 1800 021 167
TESTS
Based on JPEG files taken with the Canon EOS RP camera.
Based on CR3.RAW files converted into 16-bit TIFF format with Adobe Camera Raw.
SAMPLES
Vignetting at 15mm, f/2.8.
Vignetting at 20mm, f/2.8.
Vignetting at 24mm, f/2.8.
Vignetting at 28mm, f/2.8.
Vignetting at 35mm, f/2.8.
Rectilinear distortion at 15mm.
Rectilinear distortion at 20mm.
Rectilinear distortion at 24mm.
Rectilinear distortion at 28mm.
Rectilinear distortion at 35mm.
15mm focal length, ISO 100, 1/320 second at f/10.
20mm focal length, ISO 100, 1/400 second at f/10.
24mm focal length, ISO 100, 1/400 second at f/10.
28mm focal length, ISO 100, 1/400 second at f/10.
35mm focal length, ISO 100, 1/250 second at f/10.
Close-up at 15mm focal length, ISO 100, 1/2000 second at f/2.8.
Close-up at 35mm focal length, ISO 100, 1/2000 second at f/2.8.
Close-up at 35mm focal length, ISO 200, 1/60 second at f/5.
15mm focal length; ISO 100, 1/250 second at f/8.
Crop from the edge of the above image magnified to 100% showing traces of coloured fringing.
Crop from the centre of the above image magnified to 100%.
20mm focal length; ISO 160, 1/200 second at f/9.
Crop from the edge of the above image magnified to 100%.
15mm focal length, ISO 100, 1/400 second at f/9.
35mm focal length, ISO 100, 1/640 second at f/9.
20mm focal length, ISO 100, 1/60 second at f/11.
15mm focal length, ISO 100, 1/60 second at f/16.
15mm focal length, ISO 100, 1/20 second at f/11.
15mm focal length, ISO 400, 1/40 second at f/8.
15mm focal length, ISO 200, 1/8 second at f/16.
15mm focal length, ISO 200, 1/125 second at f/8.
15mm focal length, ISO 200, 1/125 second at f/11.
15mm focal length, ISO 100, 1/125 second at f/6.4.
28mm focal length, ISO 200, 1/25 second at f/11.
Rating
RRP: AU$3999; US$2299
- Build: 9.0
- Handling: 9.0
- Image quality: 8.9
- Autofocusing: 9.0
- Versatility: 8.9
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