Overview

The Mamiya / Sekor SX 300mm f/5.6 Auto is a compact, lightweight telephoto lens (just over 700g) with excellent build quality and a smooth focus ring. Optical performance is good, with best center sharpness at f/8 and decent corners. However, it suffers from very shallow depth of field, making focusing critical, especially on high-resolution digital backs. The ULD version offers improved chromatic aberration control and sharpness over the older Sekor C. It suits photographers seeking an affordable, compact telephoto for medium format, but requires careful focusing and fast shutter speeds to avoid camera shake.