Phase One — 55mm f/2.8 LS medium format wide-angle with built-in leaf shutter, Phase One XF mount
The Phase One 55mm f/2.8 LS is a medium format wide-angle lens developed by Schneider-Kreuznach for Phase One's digital back systems. Part of the 'Blue Ring' lens series introduced in the early 2010s, it was built around a central leaf shutter for high-speed flash sync in studio and location work.
Built for full 645-format sensors, the lens uses a Schneider-Kreuznach optical formula with a built-in leaf shutter offering flash sync at all speeds up to 1/1600s. It mounts natively on the Mamiya 645AF-derived bayonet shared by Phase One XF and Mamiya 645DF/DF+ bodies, and focuses internally without extending.
Rendering favours even, low-distortion wide-angle coverage suited to architecture and studio product work rather than dramatic subject separation. Contrast and colour are tuned to match the rest of the Blue Ring range for consistency across a multi-lens medium format kit.
Used examples circulate mainly through medium format specialist dealers, with prices staying high given the limited production run. Buyers should confirm the leaf shutter fires evenly at all speeds and that aperture blades move without hesitation, since shutter service is costly.