Pentax's leaf-shutter 6x7 standard — the SMC Takumar 6x7 90mm f/2.8 LS for high flash sync.
The SMC Takumar 6x7 90mm f/2.8 LS is a leaf-shutter standard lens for the Pentax 6x7 medium-format system, from the SMC Takumar 6x7 generation of the line. The LS suffix marks the built-in leaf shutter, which allows flash synchronisation at higher speeds than the camera's focal-plane shutter permits, a feature aimed at studio 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 90mm focal length and a maximum aperture of f/2.8. The in-lens leaf shutter is its defining feature, and the Super-Multi-Coated glass denoted by the SMC Takumar name controls flare on the near-standard field of view over the large negative.
On the 6x7 frame a 90mm sits close to a normal lens, a versatile everyday angle. The f/2.8 aperture is fast for medium format, giving some subject separation for portraits, and the leaf shutter's high flash-sync speed makes the lens a favourite for balancing flash with bright ambient light in the field.
On the used market this leaf-shutter version is more specialised and often pricier than the plain 90mm, valued by shooters who need the flash sync. Confirm the leaf shutter fires and times correctly across speeds, check 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 there.