Canon recently launched the ultra-wide zoom RF 10-20MM f/4 L IS STM lens ($2,299.00) for full-frame mirrorless cameras. The lens is meant to be a modern R-system replacement for the hugely popular EF 11-24mm L lens.

It’s a slightly niche focal length range that certainly won’t be left on your camera all the time for walking about with. However, for certain types of photography, like architecture and landscape, it really comes into its own. I was able to try out Canon’s widest zoom in its RF line of lenses and put it through a few different real-world situations.

Canon RF 10-20mm – General impressions

A quick caveat here: I am a working photographer and videographer and used this lens as part of my regular gear. I won’t be going into deep technical details. However, I can give a good idea of how this lens could be an interesting addition to any photographer’s kit bag.

The lens itself feels pretty solid, though it weighs half as much as its EF predecessor. This is great, especially as this lens could be perfect for landscape photographers who might need to carry it on long hikes. I was pleasantly surprised that I could comfortably mount it on my Ronin RS3 mini gimbal with zero problems.

Another feature of the camera is a built-in lens hood (actually really useful with such a wide angle, and there’s less chance of it being misplaced!). It also features a fast and ultra-quiet STM-focussing motor and the latest image stabilising technology to eliminate any ‘fluttering’ at the edges of the frame. By itself, it can give up to 5 stops of stabilisation and even more if paired with a camera body with IBIS.

I tested this lens out on my Canon EOS R body (which incidentally doesn’t have IBIS).

Canon RF 10-20mm – Specs

Focal Length	10-20mm
Maximum Aperture	f/4
Minimum Aperture	f/22
Lens Mount	Canon RF
Format Compatibility	Full-Frame
Angle of View	Approx. 130° 25’– 94°
Maximum Magnification	0.12x (at 20mm)
Minimum Focus Distance	0.25m (9.8 in.)
Optical Design	16 elements in 12 groups
Diaphragm Blades	9
Focus Type	Autofocus
Image Stabilization	Yes, 5 stops (6 with IBIS)
Filter Size	Rear gel holder
Dimensions (ø x L)	83.7 x 112mm
Weight	570g

Canon RF 10-20mm – Optical performance

Real estate shoot

This lens is a rectilinear lens, which means that vertical lines will remain vertical as long as the camera is straight, that is. This means that this lens is perfect for shooting architecture and interiors. For shooting in small spaces, this lens is fantastic, and the range of 10-20mm worked so smoothly to fulfill all of my needs for photographing a holiday flat rental in Valencia.

Landscape shoot

Of course, a wide-angle zoom is also going to be great for landscape photography. However, for astrophotography, I would prefer to have a wider aperture available than f/4, say down to f/2 at the very least. That being said, I tried the lens out on a short hike to a castle, and I was not disappointed.

Video shoot

The lens was also surprisingly good for video, producing nice colours and very little distortion close-up considering how wide this lens goes. I normally wouldn’t use a zoom for video. However, I couldn’t resist trying out the ultra-wide angle, especially as we were shooting in what was essentially a glorified closet.

The incredibly quiet and fast autofocus made for buttery smooth footage, and it was fantastic just to be able to concentrate on the filming and composition and almost just let the autofocus do its own thing.

Sharpness

Let’s not beat about the bush here, this is an incredibly sharp lens. Of course, it’s sharper in the centre parts of the image and does suffer from a slight lack of sharpness at the edges of the frame, but I belive that is largely due to distortion at the wider end of the zoom. And honestly, it’s not so much that anyone who isn’t pixel-peeping would notice.

Distortion/vignetting

The lens can actually apply image correction in camera if you shoot Jpeg. Otherwise, you need to rely on your post-processing software to apply the corrections. This sorts out any barrel distortion and vignetting when shooting at the widest focal lengths (and yes, the castle is tilted in real life, in case you were wondering!).

It’s pretty slick, too. It would be easy not to notice that the lens is actually sorting all of this out for you, but by turning off the auto-correction, you can see that the distortion and vignetting are both quite pronounced at the wider end of the lens.

But this is perhaps more of a feature of shooting with ultra-wide lenses than of this particular lens itself. I particularly welcome any less time I can spend in post-production, so am happy to use the auto-correction. Saying that, I did still have to correct some verticals in the holiday apartment, even though I was careful to keep my camera perfectly level while shooting.

Downsides?

Because of the round exterior of the lens plus the built-in lens hood, you aren’t going to be able to use regular filters that go on the front of the lens. Annoying if that’s how you work and you have a nice set of filters. However, there are other options, such as filters that slot between the lens and camera body or even magnetic ones that fit directly over the sensor. For me, that’s not a deal breaker.

Again, this isn’t a super fast lens, only going down to f/4. For many things, that’s not a big problem, and you’ll probably want to be shooting around the sweet spot of f/8 anyway for much of the time.

Who is this lens good for?

This lens is great for anyone who is serious about landscape photography and doesn’t need the extra wide apertures for low light. It was great to have the super wide 10mm option, particularly if you are photographing epic locations and mountains with a lot of sweeping scenery. However, I found myself wanting to hover between the 15-20mm end of the lens for much of the time.

I would find this lens far too wide to be useful for street photography unless you are concentrating on large architecture. For anything with people, there is just too much distortion for my taste, at least.

However, for shooting real estate, this lens was perfect, and really useful to have the zoom option, particularly if rooms are small. Normally, I use a 15mm prime manual focus lens, so I did find the autofocus a massive advantage, which sped up the whole process no end.

Conclusion

This lens is certainly groundbreaking, however, at $2,299, it is not cheap. Unless you have oodles of spare cash, I would only buy this lens if I was serious about shooting either landscapes or architecture/interiors. If that was the case, I would buy it in a heartbeat.

The Canon RF 10-20mm lens is a fantastic addition to the RF range of lenses that Canon offers, and honestly, there’s no substitute if you need this range of focal length. Everything works super smoothly, the fast autofocus and the lack of distortion make these ultra-wide focal lengths a joy to shoot.