Pentax's leaf-shutter 6x7 tele — the SMC Pentax 6x7 165mm f/4 LS for high flash sync.
The SMC Pentax 6x7 165mm f/4 LS is a leaf-shutter short-telephoto lens for the Pentax 6x7 medium-format system, from the SMC Pentax 6x7 generation of the line. The LS suffix marks the built-in leaf shutter, which allows flash synchronisation at higher speeds than the focal-plane shutter, aimed at portrait and fill-flash work.
This is a manual-focus lens for the Pentax 67 bayonet mount, covering the 6x7 cm frame. It has a fixed 165mm focal length and a maximum aperture of f/4. The in-lens leaf shutter is its defining feature, distinct from the faster f/2.8 non-LS 165mm, and the Super Multi Coating denoted by the SMC prefix controls flare on the telephoto field.
On the 6x7 frame a 165mm gives a classic portrait-telephoto reach, compressing perspective for flattering framing. The leaf shutter's high flash-sync speed lets photographers balance flash against bright ambient light outdoors, which is the main reason to choose the slower f/4 LS over the brighter focal-plane-only version.
On the used market this leaf-shutter telephoto is a specialist choice bought by 6x7 shooters who need the flash sync. Confirm the leaf shutter fires and times correctly across speeds, inspect for haze and fungus, and test the aperture for oil. It adapts to mirrorless via a Pentax 67 adapter, though the leaf shutter is not driven on those bodies.