The Canon RF 10-20mm f4L IS is an ultra-wide zoom for the EOS R mirrorless system that’s corrected for full-frame bodies. Yep, 10mm on full-frame, and it’s not a fisheye either. This is a rectilinear lens, which means straight lines stay straight, rather than becoming curved, making it perfect for architecture, as well as landscape and videography. 

It delivers not just the widest coverage in the RF system to date, but also becomes the World’s widest full-frame zoom with autofocus. This kind of performance doesn’t come cheap though, with the RF 10-20 costing around £2500 when launched in October 2023.

Two and a half grand is obviously a lot of money, but it’s actually a little bit cheaper than the older EF 11-24mm f4L which it effectively replaces. And while it doesn’t zoom quite as far at the long-end, it does capture a wider field of view while being considerably smaller, lighter and now also sporting image stabilisation. Find out more in my hands-on first-looks video below, or keep scrolling for the written highlights!

As an aside, cross-platform lens fans may already be aware of Laowa’s 10-18mm f4.5-5.6, which matches the full-frame coverage at the wide-end and at a much lower price of around $700 or pounds.

But this is a much simpler manual-focus lens with a dimmer aperture, no stabilisation or weather sealing, and it’s also only available in Sony, Leica-L or Nikon-Z mounts right now. 

So back to the new Canon which I had a brief chance to try out at a press briefing. Considering the extreme coverage on offer, the RF 10-20 is a surprisingly compact lens, measuring 84x112mm, including its built-in petal hood, and weighing just 570g.

This makes it roughly similar in size and weight to the RF 14-35 f4L IS, seen here on the right with its lens hood fitted. This was previously the widest lens in the RF system, and currently costs around $1500 or £1750, making it roughly half the price of the 10-20. Both lenses are miniature compared to the giant EF 11-24 f4L on the left. The new 10-20 is not only around 2cm shorter and narrower, but just under half the weight. In fact add the EF to EOS R adapter for it to work on mirrorless bodies and the physical difference becomes even more obvious.

Here’s the old EF 11-24mm adapted to the EOS R5 body where it’s clear just how hefty and front-heavy this lens is. I loved its coverage and quality when it came out in 2015, but at almost 1.2kg for the lens alone, you certainly knew you were carrying it around.

Just compare it to the new RF 10-20 here, mounted on the same R5 body and it’s obvious how much more portable and practical the new lens is in comparison.

As a member of Canon’s L series, the 10-20 is fully sealed against dust and moisture, including a rubber grommet at the mount. Here you’ll also notice a rear-mounted filter holder, as the bulbous front element and extreme coverage rule-out front-mounted screw-in filters. Like other ultra-wide lenses, the supplied cap fits over the built-in petal hood. 

There’s three rings, starting with the zoom ring closest to the body which, as you can see, extends the front element within the barrel. It’s furthest out at the 10mm focal length. Alongside the zoom ring is a very smooth, free-spinning manual focus ring, followed by a customisable RF control ring towards the end of the barrel.

There’s also switches for auto and manual focus, optical stabilisation, and a custom button which is set to AF Stop by default. Canon normally reserves these buttons for super-telephotos only, but customisation can make them useful on any lens.

In terms of focus, you’d be forgiven for assuming it’s Canon’s usual USM system, but the 10-20 becomes the first in the L-series series to employ an STM motor, possible here due to the light focusing group. It’s faster at focusing than the old EF 11-24 and smoother too which videographers will appreciate. The new lens also doesn’t reset the focusing distance, which allows it to startup faster. The closest focusing distance is 25cm.

I had a brief chance to try out a pre-production RF 10-20 to compare its coverage against the RF 14-35 and EF 11-24 lenses. To illustrate the difference here’s the 10-20 view at 10mm above, superimposed by a green and red frame, representing the widest coverage of the EF 11-24 and RF 14-35 respectively. I generated these graphics using my actual sample images, so these are the differences you’ll see in practice.

But while the 10-20 zooms wider than the other two, it won’t reach as far, so here’s how the new lens looks at its longest focal length of 20mm, above. Once again the green and red frames represent the coverage of the EF 111-24 and RF 14-35 lenses, but this time at their longest focal lengths. Clearly the 14-35 enjoys considerably longer reach than the others, not to mention the broadest range and the lowest price, but equally it’s the least wide of the three.

Just before wrapping-up, the new RF 10-20 becomes the first Canon lens to include Peripheral Control IS. This is designed to work with bodies that have sensor-shift IBIS, and claims to reduce the wobbling effect often seen in the corners of ultra wide lenses when filming video. 

I was unable to illustrate this on my pre-production lens and R5 body, but I still filmed a handheld clip for you to illustrate the potential coverage at 10mm with IBIS and optical IS enabled. Canon claims five stops of compensation on bodies that don’t have IBIS, or six for those that do.

For comparison here’s the RF 14-35 at 14mm, and while that lens also has optical IS, it’s clearly nowhere near as wide. If you’re also thinking of applying digital stabilisation, the new lens has much greater latitude for accommodating a crop. Ok, now for my verdict so far.

Canon RF 10-20mm f4L IS verdict so far

The Canon RF 10-20mm f4L is an unashamedly high-end lens aimed at those who demand the widest coverage without compromising on quality, distortion or having to lug around a hefty chunk of glass. Compared to the EF 11-24 it effectively replaces, the new 10-20 not only zooms wider and now sports image stabilisation, but is considerably smaller and lighter, making it a much more practical proposition. This is a lens you’d be happy to carry all day rather than just on special occasions, and it’ll also balance better on gimbals or a tripod.

Again this performance doesn’t come cheap, but in fairness the RF 10-20 is launched at a slightly lower price than the eight-year-old 11-24 still sells for. I know which model I’d rather have. That said, if you’re satisfied with 14mm coverage, the RF 14-35 will give it to you at half the price with the benefit of reaching comfortably further and sporting a standard front filter thread. And at the more affordable-end, it would be nice if Laowa were also able to launch an RF version of its manual focus 10-18, but restrictions are the current state of play in the EOS R system. Check back soon for my full review and sample images.