The Canon EF 40mm F2.8 STM is a very slim, very lightweight pancake-style prime lens for both full-frame and APS-C Canon DSLR cameras. It features a stepper motor for fast, quiet focus, particularly important with the contrast-detection method of autofocus used for live view and video. Its optical construction includes an aspherical element and coatings optimized to reduce flare. Its closest focus distance is a mere 30cm, and a circular 7-bladed aperture ensures pleasant rendition of out of focus areas.
The EF 40mm f/2.8 STM is a lens whose impressive image quality belies its low price and tiny size. For APS-C users it’s a tiny, inexpensive companion to a kit zoom, and on full frame it offers a great option for general shooting. It’s taken a while for Canon to come to the pancake party, but the 40mm takes its place alongside its peers as one of the best examples of its type.