Pentax SMC Pentax 67 90mm f/2.8 LS

One of two leaf-shutter ("LS") lenses in the Pentax 67 lineup (the other being the 165mm f/4 LS). The 90mm f/2.8 LS contains its own shutter mechanism inside the lens barrel, bypassing the body's focal-plane shutter when in use — this enables flash sync at all shutter speeds up to 1/500 second, vs. the body's 1/30 X-sync limit.

For studio fashion, mixed-light location work, and any photography requiring fill-flash at fast shutter speeds, the 90mm f/2.8 LS is a critical tool — the leaf-shutter Pentax 67 lenses are the only path to high-sync-speed flash on this system. Photographers shooting weddings or editorial portraiture at outdoor locations use this lens with fill-flash at 1/500 to balance ambient light against subject-side strobe in conditions where the body's 1/30 sync would force ND-filtered ambient or radically smaller apertures.

Optically a wide-normal lens — ~46mm-equivalent on 35mm — placing it just wider than the 105mm f/2.4 normal. f/2.8 maximum aperture is a half-stop slower than the 105mm but still fast for medium-format. Mounts on the inner bayonet; 67mm filter thread.