Pentax's medium-format soft-focus lens — the SMC Pentax 6x7 120mm f/3.5 Soft for portraits on 6x7.
The SMC Pentax 6x7 120mm f/3.5 Soft is a soft-focus portrait lens for the Pentax 6x7 medium-format system, from the SMC Pentax 6x7 generation of the line. Its optical design deliberately introduces controlled spherical aberration, giving a dreamy, diffused rendering that photographers use for flattering portrait and pictorial work on the 6x7 negative.
This is a manual-focus lens for the Pentax 67 bayonet mount, covering the 6x7 cm frame. It has a fixed 120mm focal length and a maximum aperture of f/3.5. The soft-focus effect is strongest at the wider apertures and reduces as the lens is stopped down, and the Super Multi Coating denoted by the SMC prefix maintains colour and contrast within the diffusion.
The soft rendering is the whole point of this lens: it wraps highlights in a gentle glow that suits portraits, weddings and pictorial subjects on the large negative. Controlling the effect through aperture selection lets the photographer dial in how much diffusion they want, from a marked halo wide open to a nearly-sharp image stopped down.
On the used market this specialist soft-focus lens is uncommon and bought by portrait and fine-art 6x7 shooters who specifically want the look. Confirm any soft-focus control ring, if fitted, moves properly, inspect for haze and fungus, and check the aperture blades are dry. It can be adapted to mirrorless through a Pentax 67 mount adapter.