CANON RF 100-500mm f/4.5-7.1L IS USM
Canon has again exploited what can be achieved in lens design with the mirrorless configuration, creating a more compact and lighter telezoom that delivers exceptional optical performance.
Canon has really got its teeth into designing lenses that make the most of the mirrorless camera configuration. The RF 100-500mm telezoom packs a lot of focal range into a very manageable lens that’s consequently hugely versatile.
Among the various incentives for ditching the longserving reflex configuration for interchangeable lens cameras is what can be achieved with lens designs once the mirror box is out of the way. The shorter flange distance – or back focus distance – makes it easier to achieve more uniform centre-to-corner sharpness and consequently there is more flexibility with what lens designers can do with an optical construction, including making them more compact.
When Canon first launched its RF mount full-frame mirrorless system, there were a couple of early lenses that looked like its optical engineers had missed that memo… the RF 28-70mm f/2.0L USM zoom for one which, at the time, we described as “truly massive, but magnificent”. Since then Canon has really started to exploit all the potential of mirror lenses, perhaps most notably with the RF 70-200mm f/2.8L IS USM zoom, which is three-quarters the weight of its EF mount cousin and delivers better optical performance in a number of key areas.
Now, Canon has done it again with the RF 100-500mm f/4.5-7.1L IS USM telezoom for which there isn’t a direct EF mount equivalent,
but the comparisons with the EF 100-400mm f/4.5-5.6L IS II USM are telling. Obviously, for starters, you get the extra 100mm of focal length (with the inevitable slight loss of lens speed), but you don’t have to pay for this with a lot of extra physical length, at least in terms of carrying and storing… the 100-500mm is just under 208mm compared to the 100400mm’s 193mm. That said, the 100-400mm zooms internally while the 100-500mm has a trombone-type mechanism, so it is quite a bit longer (roughly by 90mm) physically by the time you get to 500mm. Is this an issue? Not really, as it doesn’t upset the balance even when shooting handheld, and Canon claims it’s still been able to effectively weather-proof the telescoping barrel. Incidentally, the first version of the 100-400mm worked the same way, but Canon switched to the internal zooming arrangement with the Mark II lens – which was launched in late 2014 – to allow for weather sealing. Clearly in the intervening time, it’s been able to find a workable solution as the RF 70-200mm f/2.8 has a telescoping zoom design too, and is also fully weather-sealed. Presumably, the 100-500mm uses the same dust filter arrangement between the two barrel sections. As also part of the all-weather capability, both lenses have fluorine coatings on the exposed surfaces of the front and rear elements to help repel moisture and grease while also enabling easier cleaning.
On the scales, the RF 100500mm is actually lighter than the RF 100-400mm – 1.37kg versus 1.55kg, both minus the tripodmounting collar although, in the case of the DSLR lens, only the foot plate detaches rather than the entire ring assembly. The barrel diameters are essentially the same – 93.8mm for the 100500mm and 92.0mm for the 100400mm – so both lenses have a 77mm screwthread filter fitting. It should be noted here that the front section of the lens doesn’t rotate during zooming, so orientationsensitive filters remain in their set positions.
Thanks to its size and weight, the RF 100-500mm is quite manageable for handheld shooting, assisted by having optical image stabilisation of up to five stops of correction for camera shake (incidentally, one stop more than what’s available with the EF 100400mm’s OIS). Given neither the EOS R nor the RP have in-body stabilisation, OIS is a must for a lens that extends to 500mm. In conjunction with the IBIS in the EOS R5 and R6 duo, the correction range increases to six stops and there are five axes of movement, not just two. The OIS has three modes for shooting stationary subjects, for panning (which essentially switches off the horizontal movement) and for subjects that are moving erratically.
The main barrel tubes are magnesium alloy with, as just noted, a detachable tripod mounting collar. There are four control rings, the biggest being for zooming and it’s accompanied by a torque adjustment ring that can be rotated between ‘Smooth’ and ‘Tight’ to vary the weighting. This essentially translates into speedversus-precision, but it’s also about what feels the most comfortable to operate. As an RF mount lens, the 100-500mm also has the multifunctional Control Ring – located closest to the lens mount – which can be set to adjust apertures, shutter speeds, ISO settings or exposure compensation. Having these available on the lens itself can be a lot more convenient than referring back to the camera body, especially for ISO or exposure compensation adjustments that you’d typically make on-the-fly. The final control collar is for manual focusing and is fly-by-wire rather than mechanical, and is only active when you switch to manual focusing (but can be switched to serve as a full manual override via a setting in the R-series bodies).
There are also four switches on the lens barrel and these comprise the aforementioned AF/MF selector and a focus range limiter, plus the optical stabiliser’s on/off and mode selectors.
INNER WORKINGS
Inside, the 100-500mm has an impressive optical construction comprising 20 elements in 14 groups – one element less than the EF 100-400mm. There are a total of seven special elements, all with extra-low dispersion characteristics to minimise axial chromatic aberrations. In Canon’s optical lexicon, one of these elements is a ‘Super UD’ type and the rest are plain old ‘UD’, the initials standing for “ultra-low dispersion”.
Reducing colour fringing is a key to optimising sharpness – especially towards the edges of the frame – and also ensuring cleaner separation from the out-offocus areas. The 12-pin interface on the RF mount enables more scope for in-camera lens corrections which include vignetting and distortion, plus the Digital Lens Optimiser processing in the
EOS R bodies that additionally corrects for lateral chromatic aberrations, spherical aberrations and diffraction. Canon’s advanced Air Sphere Coating helps minimise flaring and ghosting caused by internal reflections.
The focusing system is similar to that of the RF 70-200mm f/2.8, and employs dual focusing groups, each driven by its own Nano
USM motor. This arrangement is designed to improve the optical quality at shorter focusing distances (and, again, particularly corner sharpness). However, the dual-drive arrangement also delivers increased speed while also reducing the power consumption, plus it’s smoother and quieter, both of which are advantageous when shooting video.
The minimum focusing distance is 90cm at 100mm, and then extends to 1.2 metres by 500mm to give a maximum reproduction ratio of 1:33 (i.e. one-third life size), which is virtually the same as the 100-400mm at 400mm when its minimum focusing distance is
“THANKS TO ITS SIZE AND WEIGHT, THE RF 100-500MM IS QUITE MANAGEABLE FOR HANDHELD SHOOTING, ASSISTED BY HAVING OPTICAL IMAGE STABILISATION.”
98cm. The focus range selector can be set so the minimum focusing distance becomes three metres, and the AF won’t waste time in the close-up range.
The diaphragm employs nine blades to give a rounder aperture and hence smoother out-of-focus effects. From around 200mm onward, the 100-500mm is marginally slower than the 100400mm at the same focal lengths, but it’s minimal and the step on to 500mm comes at the cost of about another half-stop’s loss.
The minimum aperture range is f/32 at 100mm to a pin-point f/51 at 500mm, by which time you’re going to well and truly need that in-camera correction for the effects of diffraction.
Should you decide that you need to go longer, the RF 100500mm is compatible with the RF mount teleconverters deliver a 1.4x or a 2.0x increase in focal length. However, they lock-out the 100mm to 300mm focal range so you effectively end up with either a 450-750mm or a 600-1000mm telezoom.
PERFORMANCE
In terms of size and weight, the 100-500mm is very similar to a 70-200mm f/2.8 in the DSLR world. It’s obviously a lot slower in comparison, but the wider and longer focal range is hugely versatile and covers a whole range of applications from portraiture to sports, action and wildlife. It can be comfortably handheld and certainly isn’t overly taxing to carry around for long periods of time or even when hiking. Better still, there are very few compromises, thanks to the optical stabilisation (further enhanced if you have an IBIS-equipped EOS R-series body), useful close-up focusing capabilities, full weather sealing and the potential for even better AF performance when used on either the R5 or R6.
The optical performance is also much less compromised than you would normally expect from telephoto zooms, especially at the longer focal lengths. Much of this is down to what’s possible with the mirrorless configuration, but it makes the RF 100-500mm much more of an all-rounder than would be the case with a DSLR equivalent. As we’ve noted elsewhere, it’s arguably the advances in lens design and performance that will be the main reason many DSLR users decide to switch to mirrorless ahead of any camera body-based benefits.
What’s most noticeable is the improvements in the uniformity of both centre-to-corner sharpness and brightness across the entire focal range. Vignetting is only very slight even when shooting wide-open and closing down a stop eliminates it completely (although the in-camera ‘Peripheral Illumination’ correction is even more effective and at any aperture). Sharpness is, put simply, exceptional with the corners holding up exceedingly well at any focal length and when shooting wide open. There is a slight fall-off beyond 300mm when shooting at the widest apertures, but it is only slight and much less than we’ve been accustomed to seeing with telezooms for DSLRs. In many cases, it just won’t be noticeable.
There’s minimal distortion with only very slight pincushiontype bending occurring between 150mm and 500mm and unlikely to be noticeable in most shooting situations. Both flare and ghosting are very effectively suppressed, as is lateral chromatic aberration, which is totally eliminated by the in-camera processing, but is still largely negligible otherwise with very slight fringing in the magenta-to-green range evident at the 500mm focal length. In pure optical terms then, Canon has done a mighty job with this lens, optimising both sharpness and contrast while successfully minimising any and all aberrations. The EF 100-400mm – while also a superb lens – just can’t match it for aspects such as corner sharpness at any focal length and the image quality at the closest focusing distances.
If you’re using the EOS R or RP then you’ll need the latest firmware upgrades to optimise the AF performance (Version 1.8.0 and 1.6.0 respectively), particularly the responsiveness and speed. And even then the subject tracking can still be a bit hit-and-miss especially with smaller subjects (we were using the EOS R) which, we suspect, wouldn’t be the case with either the EOS R5 or R6 (in fact, our online sister publication Digital Camera World reported a “practically 100 percent hit rate” with the R5 (which is not so surprising given its smarter AI-based tracking).
THE VERDICT
Obviously there are quite a few camera-related benefits derived from the mirrorless configuration, but it’s really what’s now possible with lens design that presents the most compelling arguments. And Canon is really starting to push the point with its recent RF-mount offerings, most notably the 70-200mm f/2.8 and now the 100-500mm, which is undoubtedly
Exhibit A for the prosecution. It makes the most of what’s possible with the reductions in size and weight along with enhancements to optical performance (the two being linked, of course, by the need for fewer elements). Consequently, here is a long telezoom for the full frame format that’s also an ‘everyday’ lens because it’s easy to carry, comfortable to use handheld and largely uncompromised by its focal range and length. It’s certainly not a cheap lens, but when you factor in the versatility and the promise of great results at any focal length, the RF 100-500mm is actually big on value too.
“THE OPTICAL PERFORMANCE IS ALSO MUCH LESS COMPROMISED
THAN YOU WOULD NORMALLY EXPECT FROM A TELEPHOTO ZOOM, ESPECIALLY AT THE LONGER FOCAL LENGTHS.”