Overview

The Carl Zeiss C Biogon T* 4.5/21 ZM is a compact, all-metal lens with excellent build and smooth focus/aperture rings. Optically, it offers stunningly low distortion—the best of any 21mm lens—and very crisp, contrasty performance with rich color. However, it suffers from heavy vignetting (3.2 EV wide open) and off-center color shift on digital color sensors, making it less ideal for color work on Leica M9 but excellent for black-and-white. It requires an accessory viewfinder. Best suited for black-and-white shooters or architectural photographers who prioritize distortion-free rendering.