This EF 40mm f/2.8 STM Pancake Lens from Canon is a welcome addition to Canon's line-up of EF lenses--a light, inconspicuous "normal" lens. At a featherweight 4.6 oz, this is the lightest lens (along with the 50mm f/1.8 II lens) in the EF family. It's less than one inch long, so it will never draw unwelcome attention to you when you're shooting in public. A bright f/2.8 maximum aperture allows you to shoot under pretty much any lighting conditions, and the sophisticated lens configuration, including one aspherical element, guarantees high image quality from the center to the edge of the frame. The optimized coatings used in constructing the lens greatly reduce ghosting and flare, and deliver superb color balance.
STM functionality provides quiet, smooth and continuous autofocus during video operation.