Canon RF 50mm F1.8 STM

The Canon RF 50mm F1.8 STM is a compact standard prime for the RF mount. It is built for full-frame EOS R cameras and also fits the APS-C bodies of the system, where the field of view becomes narrower. It combines a f/1.8 maximum aperture with a very small body, which makes it a typical first prime for portraits, street photography and indoor scenes. Canon announced it in November 2020, together with the RF 70-200mm F4L IS USM.

Optical design

According to Canon, the lens has 6 elements in 5 groups, including one PMo aspherical element. The aperture range runs from f/1.8 to f/22, and the diaphragm has 7 blades in a circular shape. Canon says that the lens placement and the coatings help with color balance and keep ghosting and flare low. Maximum magnification is 0.25x.

Autofocus and handling

Focusing is done by a gear-type stepping motor (STM). Canon describes the autofocus as smooth and quiet for both stills and video, including continuous AF while recording. The minimum focus distance is 0.30 m. A control ring on the barrel gives direct access to camera settings. The lens has no optical stabilizer of its own, so shake correction depends on the camera body.

Build and size

The lens weighs 160 g and measures 69.2 mm in diameter and 40.5 mm in length. The filter thread is 43 mm. Canon does not claim any dust or weather sealing on the product page, so it is best treated as a lens for normal conditions.

Where it fits

Within the RF system it sits below the RF 50mm F1.4 L VCM (580 g in our database) and the RF 50mm F1.2L USM (950 g), which are larger L-series lenses. The RF 35mm F1.8 IS STM Macro is the neighbor with a stabilizer and closer focusing, and the RF 45mm F1.2 STM offers a much wider aperture at a higher weight of 346 g. EF shooters know the Canon EF 50mm F1.8 STM, which has the same 6 elements in 5 groups but needs an adapter on mirrorless bodies.

Pros and cons

Pros

• Very light at 160 g and only 40.5 mm long
• Bright f/1.8 aperture for low light and background blur
• Quiet STM autofocus suited to video
• Control ring for direct setting changes
• 0.25x maximum magnification and 0.30 m minimum focus distance
• Small 43 mm filter thread

Cons

• No in-lens stabilizer
• Only 7 aperture blades
• No dust or weather sealing mentioned by Canon
• Not an L-series lens, so the build is plainer than on the 50mm L primes

Verdict

The RF 50mm F1.8 STM is the simple, small choice for a standard prime on Canon RF. It gives up stabilization and sealing, but it keeps autofocus, a control ring and a bright aperture in a body of 160 g. For a faster aperture or a more robust build, look at the 45mm F1.2 STM or the L-series 50mm lenses.