CLeW

The SMC Pentax-A 400mm f/5.6 is a manual-focus super-telephoto prime introduced in 1984 and produced until 2004, designed for the Pentax KA mount. It features a 7-element, 6-group optical design with Super Multi-Coating (SMC) and a 9-blade automatic diaphragm, stopping down to f/45. The lens supports 77mm filters, includes a built-in sliding hood, and comes with a tripod collar for added stability. Measuring 277mm in length, 85 mm in diameter, and weighing 1,240g, it’s a substantial lens built for serious long-reach photography. The “A” setting on the aperture ring allows full exposure automation on compatible film and digital bodies, making it more versatile than earlier K or M series telephotos. Optically, the lens delivers strong center sharpness at f/5.6, with improved edge performance when stopped down to f/8–f/11. Color rendering is typical of A-series lenses—neutral and well-balanced—with good contrast and minimal flare thanks to the SMC coatings. Chromatic aberration is present in high-contrast scenes, especially purple fringing around bright edges, but generally manageable. Bokeh is smooth and natural, especially when shooting distant subjects against soft backgrounds. The lens focuses down to 2.8 meters, achieving a 0.21x magnification ratio, which is respectable for a 400mm prime without dedicated macro capability.

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Release Date: 1984
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