Yashica's Yashinon DS-M 50mm f/1.7 — a multi-coated Japanese M42 fast standard prime.
The Yashinon DS-M 50mm f/1.7 is a Japanese fast standard prime made in M42 mount by Yashica under the Yashinon name. The DS-M designation marks the multi-coated screw-mount version, and this was the fast normal lens of the Yashica M42 range.
This is a manual-focus M42 screw-mount lens with a 50mm focal length and a maximum aperture of f/1.7, with multi-coated optics and an automatic diaphragm. Focus and aperture are set by hand on the barrel. It is a compact all-metal standard prime. Detailed element figures are not asserted here beyond the verified focal length and aperture.
As a fast standard the 50mm f/1.7 suits portraits, street and general work, with the bright aperture giving low-light capability and shallow depth of field. Yashinon standards render cleanly with pleasant character and the DS-M multi-coating gives good contrast, making it a capable and well-regarded vintage normal lens.
Used copies are affordable and fairly common. Inspect for haze, fungus and cleaning marks, confirm the aperture blades are clean and oil-free, and check the aperture-ring and focus feel. Verify the M42 mount before purchase for a screw-mount body. An M42 adapter makes it a characterful fast standard on mirrorless.