Canon's nifty fifty, the lens every EF-mount owner should have.
The Canon EF 50mm f/1.8 STM is the third generation of Canon's most popular prime lens, released in 2015. It replaced the EF 50mm f/1.8 II — Canon's entry-level 50mm since 1990 — by upgrading the mount construction from plastic to metal, replacing the micromotor with an STM stepping motor, and improving the aperture blade count from five straight to seven rounded blades. The STM motor enables quieter, smoother autofocus during video recording, which was a primary design goal of the revision. The lens became the standard first-prime recommendation for Canon DSLR users: an accessible price, natural focal length, and f/1.8 maximum aperture.
The optical design uses 6 elements in 5 groups. The 49mm filter thread is less common than Canon's standard 58mm and 77mm sizes — most standard filter collections will not fit without a step-up ring. At 160g the lens is among the lightest Canon EF primes; minimum focus distance of 0.35m is closer than most comparable standard primes, allowing informal close-up portrait work. Seven rounded aperture blades produce smoother bokeh at mid-apertures than the five straight blades of the preceding II version. The STM (Stepping Motor) autofocus is quiet and smooth, well suited to video use; it is slower than the ultrasonic motor in the EF 50mm f/1.4 USM but adequate for most stills subjects. Build combines a plastic barrel with a metal mount ring — the metal mount was a specific upgrade from the II, which used a plastic mount susceptible to wear. Super Spectra coating is applied to reduce flare.
On full-frame bodies the 50mm field of view is close to natural human vision, making the lens versatile across portraiture, documentary, and everyday photography. On APS-C bodies the 80mm equivalent suits portraiture well. Wide open at f/1.8 centre sharpness is usable but shows softness toward the edges; from f/2.8 the lens is sharp across the frame. The f/1.8 aperture provides meaningful background separation at portrait distances — a clear advantage over zoom lenses available at similar prices. The STM motor makes continuous AF in video acceptably smooth for a lens at this price, though phase-detection accuracy varies by body generation.
The EF 50mm f/1.8 STM is consistently among the most affordable used lenses available and represents one of the clearest value propositions in the Canon EF system. Condition checks should cover the AF motor function, aperture blades for oil contamination, and the metal mount for wear. Compatible with all EF-mount Canon DSLRs and with EOS R bodies via Canon's EF-RF adapter. The EF 50mm f/1.4 USM offers a faster USM motor and better wide-open performance at a higher price; the EF 50mm f/1.2L is the professional-grade option at a substantially higher price. The STM is the natural starting point.