Canon EF-S 24mm f/2.8 STM – Build and handling

The compact Canon EF-S 24mm f/2.8 STM adds little bulk to a DSLR

It may be relatively inexpensive, but this 24mm lens certainly doesn’t feel cheap. The mount is metal, and the barrel is made from quality plastic. The only external controls are the manual-focus ring, which is necessarily slim, and a small switch to change the focus mode between auto and manual.

Measuring 22.8 x 68.2mm in diameter, and tipping the scales at just 125g, this tiny lens feels like it’s barely there while you’re shooting. It works on all but the very earliest Canon DSLRs with APS-C sensors, and should be a particularly good match for the EOS 100D.

Autofocus

Tested on the EOS 70D, the 24mm autofocused consistently accurately

Driven by a stepper motor (STM), autofocus is reasonably fast and disconcertingly quiet. The motor is just about audible in a quiet room, with a high-pitched whine, but in noisier environments it can’t be heard at all. It’s also possible to adjust focus while recording video without it impinging on your soundtrack.

Manual focus is electronically, rather than mechanically coupled, meaning that turning the smoothly damped focus ring drives the AF motor of the lens. This works very well, and allows extremely accurate focusing. However, it’s only possible to adjust focus when the camera is turned on and metering activated 
by a half-press of the shutter.