Pentax's ED super-tele — the SMC Pentax 6x7 400mm f/4 ED for wildlife on the 6x7 frame.
The SMC Pentax 6x7 400mm f/4 ED is a long telephoto lens for the Pentax 6x7 medium-format system, from the SMC Pentax 6x7 generation of the line. It uses extra-low-dispersion glass, marked by the ED suffix, to control chromatic aberration at long focal length on the large 6x7 negative, aimed at wildlife and sport.
This is a manual-focus lens for the Pentax 67 bayonet mount, covering the 6x7 cm frame. It has a fixed 400mm focal length and a maximum aperture of f/4, bright for a lens of this reach on medium format. The ED glass curbs colour fringing, and the Super Multi Coating denoted by the SMC prefix holds contrast on the long telephoto field.
The 400mm reach pulls in distant subjects with strong perspective compression on the 6x7 frame, suiting wildlife, sport and distant landscapes. It is a large and heavy lens that needs solid tripod support, and the fast f/4 aperture helps with focusing and gives subject separation given the reach on so large a negative.
On the used market this ED super-telephoto is a heavy specialist item bought by dedicated 6x7 wildlife and sport shooters, and it commands high prices. Inspect the large front element for marks and haze, confirm the focus and aperture actions are smooth and dry, and look for fungus. It adapts to mirrorless via a Pentax 67 mount adapter.