The old instruction — f/8 and be there — predates autofocus and has survived it intact. The RF 28mm f/2.8 STM is the current Canon lens that most efficiently implements this philosophy. Small, sharp, negligible weight, and optically honest without aspiring to be a collector’s item. It is a working lens. At f/8 on a full-frame sensor, the 28mm focal length delivers a depth of field that runs from roughly two meters to the horizon when focused at five to six meters.