The Affordable f/1.2 Canon RF Prime: What the Canon RF 45mm f/1.2 STM Gets Right (and Wrong)

A sub-$500 autofocus f/1.2 prime sounds like a pricing error, especially in Canon RF. The real question is what you give up to get that bright aperture in a lens that stays small.

Coming to you from Dustin Abbott, this practical video puts the Canon RF 45mm f/1.2 STM in the kind of use that quickly exposes corner cutting. You hear about the size and weight first, and that part lands: it’s compact for f/1.2, and it balances like a normal walkaround prime instead of a front-heavy specialty lens. Abbott also covers the build honestly, with engineered plastics, a metal mount, and a simple control layout that includes an AF/MF switch and a control ring. The lens focuses internally but you can see the front group moving, which changes how you think about dust and moisture when there’s no sealing. If you tend to shoot in rough weather, the suggestion to add a 67mm protection filter is less about image quality and more about keeping the front assembly from feeling exposed.

Autofocus gets the kind of mixed report you expect from an STM design that’s trying to behave like something more premium. Abbott tests it on a Canon EOS R5 and describes a start-up hesitation before the lens commits to the move, plus some audible whirring that reminds you this is not a silent pro motor. For stills, the takeaway is reassuring: accuracy held up even at f/1.2, and the lens can land focus where it needs to on eyes when depth of field is thin. For video, the behavior shifts, with smoother focus pulls but a noticeable delay between input and response, which can make simple hand-to-face moves feel oddly behind. Abbott points out focus breathing and responsiveness limits, but also hints at a benefit if you hate twitchy tracking when you’re moving around a subject.

Where the video gets interesting is the gap between the spec sheet promise and what the optics actually do. Abbott walks through a simple design and then starts naming the compromises you usually only tolerate when you’re chasing a specific look. Distortion and vignetting are heavier than you’d expect for a 45mm, to the point where corrected and uncorrected frames don’t match in mood. Chromatic aberration shows up both in front of and behind the focus plane, and it can paint edges in bright magenta and green when you’re wide open. Resolution is the other pressure point: the center can look usable at f/1.2, but the contrast is low, and the corners can fall apart until you stop down hard. If you shoot portraits, that weakness is not automatically fatal, because corners rarely matter when faces live near the center, and the slightly hazy rendering can be flattering when you don’t want hyper-detailed skin.

Abbott doesn’t treat the lens like a pass/fail chart exercise, which is the right approach for something that’s clearly chasing “character” more than perfection. He shows how stopping down changes the personality, with a real jump in crispness as you move past the widest settings and a more dependable look as you get into mid apertures. He also flags two practical limitations you’ll want to hear in full: close-focus ability is not a strength, and flare can get ugly when you shoot into bright light, especially without a hood. The video also tees up comparisons that help you decide whether this lens fills a real gap or just tempts you with f/1.2, including the Canon RF 50mm f/1.4 L VCM for speed and responsiveness. Check out the video above for the full rundown from Abbott.