Canon's CN-E 15.5-47mm zoom, along with it's sister lens the 30-105mm, are perfect for high-end doc shoots. They're incredibly sharp, have 11 iris blades and a consistent max. aperture of T2.8, and are identical color matches to one another. They both offer a fairly safe, neutral look with just a touch of warmth on skin tones, and have relatively minimalistic flares. Their weight is light enough for longer stints of handheld work while still having enough heft to allow for smoothness in those movements.