Visually, Canon’s EF 40mm pancake lens looks virtually identical to the EF-S 24mm, apart from the numbers printed on the barrel
A s well as the EF-M 22mm and EF-S 24mm APS-C format pancake lenses reviewed, there’s also an EF 40mm f/2.8 STM pancake lens for full-frame DSLRs. It has the same dimensions as the EF-S 24mm, at 68x23mm, and is a mere 5g heavier. When using the 40mm on a full-frame body, the viewing angle is almost the same as when using the 24mm lens on an APS-C body, at 59 degrees and 57 degrees respectively. Naturally, that’s a little narrower than using a preferred 35mm lens on a full-frame camera, or the EF-M 22mm on an EOS M mirrorless APS-C format camera.