Enticingly, at the time of launch, the Canon EF 11-24mm f/4L USM is the widest full-frame lens with autofocus. It’s suitable for a range of uses such as landscape, architectural, and interior photography, and according to Canon, it outperform its EF-mount predecessor.
The lens comprises 16 elements in 12 groups, including aspherical and both UD (ultra-low dispersion) and Super UD glass elements. Canon has also applied anti-reflective coatings to reduce flare and ghosting.
Canon has used an advanced rectilinear design which enables a 130-degree angle of view with minimal distortion so that straight lines remain straight, even at the edges of the frame.
The lens uses an STM system for autofocusing, which is a first for Canon’s L-series. This is optimised for linear focus, which is good news for videography. The lens also features a positioning sensor, which eliminates the need for the lens to reset when the camera is powered on or off, making it slightly quicker to use. Full-time manual focusing is also available in case the focus needs a tweak.
There’s a closest focusing distance of 25cm throughout the focal length range. Focusing at this point delivers a magnifications of 0.12x at the 20mm end and 0.06x at the 10mm end.
As indicated by the ‘IS’, the RF 10-20mm f/4 L IS STM has built-in image stabilisation. In this instance it offers up to 5 stops of shake reduction, or up to 6 stops when paired with Canon’s R-series cameras that have in-body stabilisation (IBIS).
Additionally, the lens includes a new feature called Peripheral Control Image Stabiliser, which is basically a new algorithm designed to reduce motion blur at the edges of the frame. It’s especially useful for ultra-wide-angle shots and works in both video and stills mode.
While screw-on filters are not compatible due to the lens’s bulbous front element, a gelatine filter holder is present behind the rear element.
As you’d expect with a Canon L-series lens, the RF 10-20mm f/4 L IS STM is dust and water-resistant.