Pentax's medium-format wide-angle — the SMC Pentax 6x7 45mm f/4, rectilinear on the 6x7 frame.
The SMC Pentax 6x7 45mm f/4 is a rectilinear wide-angle lens for the Pentax 6x7 medium-format system. It sits in the SMC Pentax 6x7 generation of the line and gives the large 6x7 negative a wide field of view with straight, corrected lines, the counterpart to the fisheye at a similar focal length.
This is a manual-focus lens for the Pentax 67 bayonet mount, covering the 6x7 cm frame. It has a fixed 45mm focal length and a maximum aperture of f/4. The Super Multi Coating denoted by the SMC prefix reduces flare and internal reflections, which matters for a wide lens that often takes in bright sky or light sources.
As a corrected wide-angle it keeps verticals and horizons straight, suiting landscapes, interiors and architecture on the big negative where the resolution rewards a well-corrected optic. Depth of field is broad at this focal length, and stopping down toward the middle apertures evens out sharpness across the wide field for demanding subjects.
On the used market this wide is sought by 6x7 landscape and architecture shooters and is scarcer than the standard primes. Check the front and rear elements for haze and scratches, look for fungus inside, and confirm the aperture blades are dry and the focus helicoid turns smoothly. It can be used on mirrorless through a Pentax 67 adapter.