Canon Shows Off RF 10-20mm Full-Frame Zoom

Canon's newest zoom lens addresses one of the long-running problems with wide-angle photography: lens size. Zooms that cover an extreme angle are often oversized. The RF 10-20mm F4 L IS STM bucks that trend—at around 4.4 by 3.3 inches (HD) and 1.3 pounds it's half the weight of the EF 11-24mm F4 L USM for SLRs, with optics that see 25% percent more of a scene.

The Mirrorless Size Advantage, Realized

Like the other major players in the photo industry, Canon's camera business is now centered around mirrorless cameras, not SLRs. Models in its EOS R line place the image sensor right behind the lens mount, a technical detail that makes it easier for engineers to make optical formulas that see a broad view. We've already seen other camera makers use this to their advantage, the Sony FE 12-24mm F2.8 GM is the obvious example.

Canon opted for a wider angle of view and F4 optics over making an extremely wide F2.8. At 10mm, a lens covers about a 50% broader view than at 12mm, something you can use to your advantage to get landscapes with an epic view or unique perspectives on interiors. The RF 10-20mm draws scenes with a rectilinear project too, so it's something you can use for real estate or architecture. This isn't a fish-eye like the old EF 8-15mm zoom for SLRs.

Image stabilization is included in-lens, even though Canon puts in-body stabilization in most of its full-frame cameras. It's not something we usually think of as necessary for a wide lens, it's easier to get away with a lengthy shutter speed boosted by IBIS. Canon tells us it puts IS in this lens to improve corner performance in these situations, as IBIS alone may smear during a long exposure. A rear filter hold is included so you can add a gel neutral density; this is necessary, as the bulbous front element and built-in hood preclude threaded filters.

Canon uses a stepping motor (STM) for focus, an uncommon choice for an L series lens. STM focus is quiet and supports smoother transitions than linear drive motors. We don't see the 10-20mm as a lens for action photography, however, and based on experience with other lenses expect its motor to be just fine for photo and video work. It's something we'll look at when we review the lens.

L Series Fit and Finish

The RF 10-20mm is part of Canon's L series, its designation for pro-line lenses. As such, it includes a good array of on-barrel controls along with some weather protection. Canon bills it as being dust and water resistant, and the front glass has anti-smudge fluorine so you won't have to sweat the inevitable fingerprints too much.

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The L designation goes beyond the exterior. Inside, the lens has a complex 16-element/12-group optical formula. It includes several exotic elements, including one super ultra dispersion (UD), three UD, and three aspheric.

The lens is set for November availability at a $2,299 retail price.