This is our widest zoom that covers ⅔” sensors.  It’s great for Doc shoots where you’re crammed into a tight room but still need to include everybody.  As with most B4 lenses, the safety glass is mounted in the hood, since the outer lens element is so convex.  There’s a dial to easily adjust zoom speed.  As with all our B4 lenses (except our cinema line), it includes a 2x Extender that can be snapped in and out to quickly double the focal length at the loss of a stop of light.