This lens, the 24mm and the 85mm are the three best lenses to use in low light. This lens has a brilliant soft and dreamy look shooting wide open . Canon did a really nice job maintaining the image sharpness while shooting wide open. It is lenses like this that make the use of shooting with black pro mist, digital diffusion, or the black magic filter.
This entire lens set is in EF with focus, iris and zoom gears and 77mm inner diameters and 80mm outer diameters.
They will cover Full Frame, Super 35mm and m4/3 sensors.