Canon RF 24-105mm f/4 L IS USM lens

In summary

Photographers who have invested more than AU$3000 in the EOS R body will naturally expect a lens that can match it. Fortunately, the RF 24-105mm f/4L IS USM can do that – especially around the centre of the frame – with most focal length settings once the lens has been stopped down a little.

Other features arguing in favour of this lens are its relatively compact size and light weight as well as its versatility, which will make it appealing to travellers as well as photographers embarking on their first steps towards building a full-frame mirrorless system. In essence, it’s a very appealing, general-purpose walkaround lens.

Full review

If you had to choose just one lens to go with a ‘full frame’ camera, the 24-105mm zoom is the one most photographers would select. So it’s nice to see Canon offering the RF 24-105mm f/4 L IS USM lens with its new EOS R mirrorless camera. Compact and relatively lightweight, this lens boasts the same constant f/4 maximum aperture as its EF mount predecessors. But it adds a new, customisable Control Ring, which can be configured to adjust exposure settings like aperture, ISO and exposure compensation.

Angled view of the RF 24-105mm f/4 L IS USM lens without end caps or the supplied lens hood. (Source: Canon.)

The optical design of the RF 24–105mm f/4 L IS USM lens is relatively complex, with 18 elements in 14 groups and featuring large diameter rear elements to capitalise on the short flange back of the RF system. There are three aspherical elements to correct for astigmatism, spherical aberration, and geometric distortion and one UD (Ultra-low Dispersion) element to minimise chromatic aberrations.

The optical design of the RF 24–105mm f/4 L IS USM lens showing the location of the exotic elements and the focusing and stabilisation lenses. (Source: Canon.)

Stabilisation is provided by moving a Compensation Optics group in the centre of the lens. The system is CIPA rated for up to five stops of shake correction when shooting stills or video clips.

Focusing is controlled by a single lightweight focusing element that is moved by a new thin-type Nano USM (ultrasonic motor) guided by a control bar.  Proprietary Air Sphere Coating (ASC) significantly reduces ghosting and flare, while fluorine coatings on the front and rear surfaces prevent dirt and dust from sticking to the lens and make it easy to clean.

The positions of the dust- and drip-resistant seals in the RF 24–105mm f/4 L IS USM lens.  (Source: Canon.)

Dust- and water-resistant sealing prevents contaminants from entering the camera via the lens mount, switch panel and all rings, enabling it to be used in challenging conditions. This lens also features L series-level vibration shock resistance in the lens barrel.

A nine-bladed iris diaphragm closes to a circular aperture that produces soft and attractive blurred backgrounds. The EOS R’s 12 pin communication system enables data from RF lenses to be transferred automatically to the in-camera Digital Lens Optimizer, which can correct common aberrations and prevent image deterioration, especially around the edges of the image frame when shooting with large apertures.

The camera can also display lens information in the viewfinder, making it easy to confirm the lens’s focal length, focussed distance and depth-of-field without looking away from the subject. Focusing is internal, enabling hassle-free use of angle-critical filters and ensuring no air or dust gets sucked in while the lens is being focused.

Who’s it for?
As the only (so far) kit lens available for the EOS R camera, the RF 24-105mm f/4 L IS USM will be a natural first choice for buyers of the new camera. Specifications-wise, it’s an impressive general-purpose lens that’s tailor-made for the camera and addresses the lack of stabilisation in the camera body.

While fairly pricey for a zoom lens, the relatively light weight and compact size of lens make it ideal for travel photography, where it can be used for both stills and video shooting. Its focal length range can span genres from landscape and architectural photography through to portraiture, making it handy for shooting weddings, parties, events, documentaries, interviews, lifestyle, fashion and street photography.

Use longer focal lengths for tightly-framed portraits and shorter ones for groups and environmental portraits. The 105mm focal length is also suitable for some sports. This lens will also suit photojournalists and some types of commercial photography, among them product and food photography and interior scenes.

Build and Ergonomics
This lens carries the ‘Made in Japan’ label, which represents high build quality. It appears to have a solid metal outer barrel with a tough, matte black polycarbonate cladding. The inner barrel appears to be made from polycarbonate and it extends by approximately 45 mm when the lens is zoomed in from 24mm to 105mm.

The front of the inner barrel flares out slightly and includes the bayonet mount for the petal-shaped lens hood. Its inner surface is threaded to accept 77 mm diameter filters. The inner barrel doesn’t rotate during focusing or zooming allowing hassle-free use of angle-critical filters.

The Control Ring is located at the front of the outer barrel, just behind the red branding ring. It’s 10 mm wide and completely covered with a fine texturing to ensure a secure grip and provide an easily-distinguished feel. The ring turns through 360 degrees and has audible click stops to make setting the programmed function easy.

Roughly 5 mm back from the Control Ring is the focusing ring, which is 19 mm wide and has a fine ridging on its grip band. Because the focusing  motor is driven from the camera, it turns through 360 degrees when power is off and provides little tactile feedback when the camera is powered-up. A Focus Guide and two levels of peaking displays provide additional manual focusing assistance to the AF point displays on the camera’s EVF and monitor screens.

The zoom ring is located immediately behind the focusing ring. It’s 25 mm wide with all but a 4 mm wide strip around the trailing edge covered by rubber with relatively thick ridges. The trailing edge is stamped with focal length marks for the 24mm, 35mm, 50mm, 70mm, 85mm and 105mm settings, which line up against a white mark on the fixed section of the outer barrel behind the ring.

The zoom ring turns through about 80 degrees with hard stops at each end of its range. It is much stiffer than the other two rings and was able to stay in place when the camera was carried with the lens facing downwards. The fixed section of the lens barrel behind the zoom ring carries a zoom lock on the right hand side plus AF/MF and Stabiliser on/off sliders on the left.

There are no distance and depth-of-field scales and no reproduction ratio display or IR focus index. Fortunately, most of this data can be displayed in the camera’s EVF or on the monitor screen.

The coating on the outer barrel slopes in to end at a 4 mm wide metal section of the lens barrel, which marks the edge of the lens mount. The mount itself is solid chromed metal with a visible gasket that is part of the weatherproofing.

The lens is supplied with front and end caps plus a petal-shaped lens hood that attaches via a bayonet fitting and has a locking button to keep it in place. A soft carrying pouch is also provided.

Performance
Overall performance was very good for a kit lens, although not quite as spectacular as the RF 50mm f/1.2L USM lens. Our Imatest tests showed the review lens to be capable of delivering higher than expected resolution with JPEG files, although only near the centre of the frame and not at the two longest focal lengths.

The best results were obtained between f/4.5 and f/8, with a significant drop in resolution due to diffraction at f/16. The graph below shows the results of our tests.

Because the EOS R automatically corrects chromatic aberration in JPEGs, we have used the data from CR3.RAW files to produce the graph of the results of our tests below. It shows lateral chromatic aberration ranged mostly within the ‘low’ band which lies between the red and green lines.

The graph of our test results for uncorrected CR3.RAW files.

For JPEG files, the results fell within the lower third of the ‘negligible’ band, indicating this aberrations is effectively corrected in the camera. We found no coloured fringing in test shots with  JPEGs confirming this assessment.

The graph of our test results for JPEGs, which are automatically corrected in-camera.

Aberrations like vignetting and distortion are also corrected automatically in JPEGs so we had to assess raw files to determine whether they were significant. Vignetting was obvious as corner-of-frame darkening at the four focal lengths we tested: 24mm, 50mm, 70mm and 105mm. It was most noticeable at the 24mm and 105mm focal lengths.

Uncorrected raw files also showed slight barrel distortion at the 24mm focal length but this quickly morphed into pincushion distortion at 50mm and pincushioning remained through to 105mm. This is not unusual with kit zooms and is easy to correct when converting raw files into editable formats.

The review lens was remarkably resistant to ghosting and flare and we were unable to force it to produce either in the test shots we took. Close-up capabilities were good with longer focal lengths, with the 105mm setting enabling some nice close-ups of flowers to be taken at wide aperture settings.

Bokeh tended to be smooth and attractive, particularly at longer focal lengths. However, these settings could bringing more of the subject’s background into focus as the lens was stopped down, instead of equalising sharpening on either side of the selected area. Wider angles of view were not affected.

Autofocusing was generally fast and very quiet and the built-in stabiliser was quite efficient, although we couldn’t always achieve the claimed five stops of shake correction. Nonetheless, we were able to shoot hand-held at 24mm with exposures as slow as half a second and obtain at least 50% of usable shots, which is pretty impressive.

Conclusion

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