Canon RF 28-70mm f/2L USM lens
In summary
Although it encompasses a zoom range suited to general purpose photography, the RF 28-70mm f/2L USM lens is most suitable for wedding and event photographers where its fast maximum aperture makes it more versatile than smaller, slower lenses.
The 28mm wide-angle setting is a bit limited for landscape photography while the 70mm may be a bit short for portraiture – but either would be usable in some situations. It’s a bit big and heavy to take bushwalking or use for travel; there are plenty of lighter, more suitable alternatives.
That said, if you don’t need to lug it far, the weatherproofing would come in handy when working outdoors. It could also be used for documentary photography or photojournalism and shooting theatre performances, fashion and some sports, particularly in low light levels.
The 70mm focal length can provide a very mild perspective compression for portraiture as well as some types of landscapes, while the wide f/2 maximum aperture could be great for photographing the night sky. Product photographers could also benefit from the differential focusing the f/2 maximum aperture allows.
Full review
The RF 28-70mm f/2L USM lens was announced on 5 September 2018 so it’s taken a while to reach our desk. Designed – and priced – as a premium lens it boasts extensive weatherproof sealing, a sophisticated optical design and a nine-bladed iris diaphragm that closes to a circular aperture to produce attractive bokeh, taking advantage of its fast and constant f/2 maximum aperture. As befits its status, this lens is supplied with a purpose-designed hood plus a soft carrying pouch.
Angled view of the RF 28-70mm f/2L USM lens, shown without its front cap and lens hood. (Source: Canon.)
Although slightly shorter at the wide-angle end than conventional 24-70mm EF-mount lenses, the RF 28-70mm is much larger and heavier than the nearest EF equivalent, the EF 24-70mm f/2.8 L II USM. It’s also almost double the price, probably because the extra stop of lens speed requires much more glass.
This cutaway view of the lens shows some of the complexity of its optical design. (Source: Canon.)
Predictably, the optical design of this lens is complex, with 19 elements in 13 groups, including four aspherical elements (two of them ground, rather than the cheaper and more common glass-moulded alternative) plus three ultra-high dispersion (UD) elements (one of them Super UD). Air-Sphere Coating (ASC) has been applied to one surface with sub-wavelength coating (SWC) on another to minimise the effects of ghosting and flare.
The optical diagram for the RF 28-70mm f/2L USM lens showing the positions of the exotic glass elements. (Source: Canon.)
Autofocusing is driven by a ring-type ultrasonic motor, which operates smoothly and quietly and provides precise focus control with low power consumption to maximise the camera’s battery life. Focusing is internal, which means there’s no rotation as the lens is focused so no external contaminants (dust or moisture) can be sucked in.
For such a pricey lens it may appear surprising this lens is not stabilised, although adding an IS lens group would increase its weight and the complexity of the optical design. Fortunately, users can take advantage of the IBIS systems in the EOS R5 and R6 cameras, for which this lens would be a good match.
This diagram shows the positions of the weather-resistant seals that keep dust and moisture out of the lens. (Source: Canon.)
The lens is supplied with the usual front and end caps plus a petal-shaped EW-103 lens hood (shown below). A soft carrying pouch is also provided.
The EW-103 lens hood. (Source: Canon.)
Who’s it For?
One the basis of price alone, this lens is most likely to be bought by professionals – and niche professionals to boot. Although it encompasses a zoom range suited to general purpose photography, it’s most suitable for wedding and event photographers where its impressive size will impress clients and its fast maximum aperture makes it more versatile than smaller, slower lenses.
The 28mm wide-angle setting is a bit limited for landscape photography while the 70mm may be a bit short for portraiture – but either would be usable in some situations. It’s a bit big and heavy to take bushwalking or use for travel; there are plenty of lighter, more suitable alternatives.
That said, if you don’t need to lug it far, the weatherproofing would come in handy when working outdoors. It could also be used for documentary photography or photojournalism and shooting theatre performances, fashion and some sports, particularly in low light levels.
The 70mm focal length can provide a very mild perspective compression for portraiture as well as some types of landscapes, while the wide f/2 maximum aperture could be great for photographing the night sky. Product photographers could also benefit from the differential focusing the f/2 maximum aperture allows.
Build and Ergonomics
Size and weight aside, the RF 28-70mm lens is very solidly built and there’s an obvious rubber seal around the lens mount that is wide enough to keep out moisture and dust. Canon doesn’t specify what the lens barrel is made from, although it’s undoubtedly some kind of metal (probably magnesium alloy) – or if not that, very high-quality engineering polycarbonate – but its matte black coating looks businesslike and smart.
Like other RF lenses, the RF 28-70mm lens has three rotating rings. The programmable control ring, which is present in all RF lenses, is located behind a thin red ‘branding’ ring approximately 19 mm back from the front of the outer barrel. It’s completely clad in fine hatching to provide a secure and comfortable grip and has soft click-stops to make precise adjustments easy.
Five millimetres behind it is the focusing ring, which is 20 mm wide and is covered by a narrowly-ridged rubber grip band. Since focus is driven from the camera, this ring can be rotated full circle when power is off.
Behind the focusing ring is a 25 mm wide, slightly in-curved band that separates the focusing ring from the zoom ring to its rear. The zoom lock is located on this section of the lens barrel.
The zoom ring is approximately 26 mm wide, with a 20 mm wide band of wider rubber ridging encircling its leading edge. The un-ridged trailing edge carries stamped marks for the 28mm, 35mm, 50mm and 70mm focal length settings. The inner barrel extends by about 20 mm when the lens is zoomed from 28mm to 70mm but it doesn’t rotate, making this lens usable with angle-critical filters.
The outer barrel slopes inwards from the edge of the zoom ring grip band finishing in a 10 mm long flat section that ends in a very solid metal lens mount. There is no distance scale or depth of field indicator but Canon’s EOS R cameras can display this information in their EVFs. The lens is manufactured in Japan.
Performance
The review lens turned in some impressive results in our Imatest tests, even for JPEG files, where the resolution in the central area of the frame comfortably exceeded expectations for the test camera’s image sensor from f/2.2 through to f/8 at 28mm and f/2.5 to f/8 for the remaining focal lengths. Even higher resolution was obtained with CR3.RAW files, while edge resolution was able to meet expectations from f/2.8 through to f/8. This indicates potential for extremely high resolution of fine details.
Corner softening was present across the zoom range but to a degree that would likely be irrelevant to most potential purchasers. The graph above shows the results of our tests.
Lateral chromatic aberration was also very low in JPEG files, which are corrected automatically in the camera. With uncorrected CR3.RAW files, lateral CA hovered around the 0.04 border between negligible and low CA, which is also very good for a lens of this type.
The results of our JPEG tests are shown in the graph above. We found no evidence of coloured fringing in our test shots with either JPEG or raw files.
Rectilinear distortion was also remarkably low for a modest wide-to-short telephoto zoom lens. Very slight barrel distortion was present in uncorrected raw files at 28mm along with a similar level of pincushion distortion at 70mm – but you had to look very hard to see them.
Vignetting was present at f/2 in uncorrected raw files at all focal lengths but, again, although visible it was not as severe as would normally be expected from a lens in this category. Fortunately, it’s greatest in the extreme corners of the frame and doesn’t intrude into the centre.
Vignetting tends to vanish when the lens is stopped down to f/2.5 or f/2.8, although distortion can’t be corrected by stopping down. Both vignetting and distortion can be corrected automatically with settings in the camera’s menu, which makes these aberrations largely irrelevant.
The review lens handled strong backlighting extremely well and proved highly resistant to ghosting and flare. This indicates effective light transmission, which will be appreciated by any videographers who choose this lens.
Bokeh was quite smooth and attractive, despite a slight tendency to outline the brightest highlights. But even here, the outlines were pleasingly softened.
Autofocusing was generally fast and very quiet. The review lens was also quick to lock onto moving subjects and subject tracking was competently handled.
Conclusion
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SPECS
Picture angle: 65 to 29 degrees horizontally
Minimum aperture: f/22
Lens construction: 19 elements in 13 groups (including 1 aspherical element), Air Sphere coating
Lens mounts: Canon RF mount
Diaphragm Blades: 9 (circular aperture)
Weather resistance: Dust and moisture resistant
Focus drive: Ring ultrasonic motor
Stabilisation: No
Minimum focus: 39 cm
Maximum magnification: 0.09x (28mm) to 0.18x (70mm)
Filter size: 95 mm
Dimensions (Diameter x L): 103.8 x 139.8 mm
Weight: 1430 grams
Standard Accessories: Front and end caps, EW-103 lens hood, LP1424 soft pouch
Distributor: Canon Australia; 1800 021 167
TESTS
Based on JPEG files captured with the EOS RP camera:
Based on CR3.RAW files recorded at the same time.
SAMPLES
Vignetting at 28mm, f/2.
Vignetting at 35mm, f/2.
Vignetting at 50mm, f/2.
Vignetting at 70mm, f/2.
Rectilinear distortion at 28mm.
Rectilinear distortion at 35mm.
Rectilinear distortion at 50mm.
Rectilinear distortion at 70mm.
28mm focal length, ISO 100, 1/250 second at f/7.1.
35mm focal length, ISO 100, 1/200 second at f/7.1.
50mm focal length, ISO 100, 1/250 second at f/7.1.
70mm focal length, ISO 100, 1/250 second at f/7.1.
Close-up at 28mm, ISO 100, 1/4000 second at f/2..
Close-up at 35mm, ISO 100, 1/4000 second at f/2.
Close-up at 50mm, ISO 100, 1/4000 second at f/2.
Close-up at 70mm, ISO 100, 1/4000 second at f/2.
Portrait shot, 70mm focal length, ISO 100, 1/500 second at f/2.2.
Portrait shot, 70mm focal length, ISO 100, 1/320 second at f/2.2.
Strong backlighting; 28mm focal length, ISO 100, 1/640 second at f/9.
Crop from the above image at 100% magnification showing no visible coloured fringing.
Strong backlighting; 70mm focal length, ISO 200, 1/160 second at f/8.
Crop from the above image at 100% magnification showing no visible coloured fringing.
28mm focal length, ISO 100, 1/640 second at f/9.
28mm focal length, ISO 100, 1/1000 second at f/9.
46mm focal length, ISO 200, 1/125 second at f/3.2.
Wide dynamic range subject, JPEG file; 70mm focal length, ISO 100, 1/200 second at f/4.5.
28mm focal length, ISO 100, 1/200 second at f/5.
70mm focal length, ISO 100, 1/160 second at f/4.
70mm focal length, ISO 200, 1/125 second at f/3.5.
70mm focal length, ISO 100, 1/200 second at f/4.5.
70mm focal length, ISO 160, 1/125 second at f/3.5.
70mm focal length, ISO 200, 1/100 second at f/4.
30mm focal length, ISO 200, 1/60 second at f/4.
70mm focal length, ISO 100, 1/200 second at f/5.6
28mm focal length, ISO 100, 1/200 second at f/8.
Rating
RRP: AU$4399; US$2999
- Build: 9.0
- Handling: 8.8
- Image quality: 9.0
- Autofocusing: 9.0
- Versatility: 8.8