The Canon EF-S 24mm f/2.8 STM is the only prime lens that Canon produces specifically for APS-C format DSLRs. You could also use a full-frame compatible 24mm lens, but this dinky optic has a lot going for it. As a pancake lens it’s compact and lightweight at 68x23mm and 125g. That makes it stealthy for street photography, especially when mounted on one of Canon’s smaller cameras like the 250D or 2000D.
With an effective focal length of 38.4mm in full-frame terms, the lens gives a natural perspective that’s very close to that of the favoured 35mm on a full-frame camera. Autofocus comes courtesy of a gear type STM (Stepping Motor) system. Unlike the lead-screw-type STM, more often used in zoom lenses, gear wheels are used to drive focusing. While this makes the system slightly slower and more audible, rather than it being almost silent in operation, this is a trade-off for the fact that the autofocus assembly is smaller, enabling the lens to be more compact. The inner barrel of the lens extends when focusing to shorter distances, but doesn’t rotate.
Like other STM lenses, manual override of autofocus and fully manual focusing are available via an electronically coupled focus ring. Unless the camera is switched on and focusing is activated, for example after a light press of the shutter button, manual override is unavailable.
The lens punches above its weight in terms of image quality, with stellar sharpness, negligible colour fringing and little barrel distortion. Overall, it’s an ideal lens for street photography on APS-C DSLRs. Despite the lightweight build, the mounting plate is metal rather than plastic, and the narrow manual focus ring is mounted at the front of the outer barrel. The lens handles nicely – as we’ve mentioned it pairs well with smaller DSLRs in terms of size, weight and form factor. Practically everything about it is small – including the 52mm filter thread – so it’s a great choice for the photographer who likes to travel light.