Image: Canon Europe · source

Canon RF 50mm F1.8 STM

Canon · Budget

A tiny, light 50 mm f/1.8 prime for Canon RF cameras, matching the Canon bodies in this catalogue.

Expert pick · Digital Camera World, Dec 2020

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We have not tested it ourselves: strengths and weaknesses below come from the tests cited.

Why Railfans Carry It

Zooms give reach; a fast prime teaches composition. On a full-frame body the 50 mm angle is a natural view for a locomotive on the next platform or a station concourse, and on an APS-C body such as the R10 or R50 it frames like a short telephoto. The f/1.8 aperture helps in dim stations and at dusk, where a kit zoom runs out of light. At 160 g it is also an easy second lens to carry alongside a telephoto zoom on a long day.

In the Field

Leave it on the camera as a platform and station lens. Shoot wide open for detail shots of a number board or signal, stop down for sharper full-train portraits. The control ring doubles as a focus ring through a switch. Expect focus breathing in video, a faint motor sound on internal microphones, and no weather sealing, so keep it dry. It does not replace a telephoto for trackside shots: pair it with a zoom such as the RF-S 55-210. Canon describes a gear-type stepping motor, so continuous focus stays smooth on a train rolling into the platform. The minimum focusing distance of 0.30 m also allows close-ups of a locomotive badge or a signal lens.

Strengths and Weaknesses

Expert pick · Digital Camera World: Digital Camera World gave it top marks as an affordable, compact standard prime with image quality that rivals far pricier lenses in places, noting only the lack of weather sealing. Read the review

Strengths

Compact and light enough to leave mounted
Image quality that holds up in tests across apertures
Fast aperture for dim stations
Quiet STM focusing
Better built than the EF predecessor

Weaknesses

Not weather sealed
Focus breathing and slight motor noise in video
Mid-frame sharpness softer than edges in lab testing
No image stabilisation in the lens

Key Specifications

Canon RF 50mm F1.8 STM — key specifications
Specification	Value
Mount	Canon RF
Weight	Approx. 160 g
Dimensions	Approx. 69.2 x 40.5 mm (diameter x length)
Filter size	43 mm
Diaphragm blades	7
Minimum aperture	f/22
Lens construction	6 elements in 5 groups
Maximum magnification	0.25x
Minimum focusing distance	0.30 m

Who It’s For

Beginners on a Canon RF body who want a first prime to learn composition and low-light shooting at an affordable cost. It is a lens for learning, not a lens for every task: its fixed angle makes you move your feet to frame a train, which is a good habit. If most of your shots are of moving trains from a distance, put a telephoto zoom first and add this prime for dusk and station work. Its 43 mm filter thread also keeps a protective or polarising filter small and light.

Alternatives

Canon RF-S 55-210 gives the reach for trackside shooting that a 50 mm prime cannot. The RF-S 18-45mm kit zoom supplied with the R10 and R50 covers wide to short telephoto, but at its long end it opens only to f/6.3, several stops slower than this prime, which shows on a dark platform or under a station roof.