Best portrait lens for the pentax k 3 mark iii monochrome?

For portraits on the K-3 Mark III Monochrome, I'd start with a fast prime. Its sensor is APS-C, so a 50 to 55mm lens frames like a classic portrait focal length, and f/1.4 gives you the soft background that makes a face stand out.

• Pentax HD D FA* 50mm f/1.4 SDM AW: my first pick, the most versatile of the three.
• Pentax smc DA* 55mm f/1.4 SDM: a little longer, so you can step back a bit more.
• Pentax HD D FA* 85mm f/1.4 ED SDM AW: frames like 128mm, so it's for tight head-and-shoulders work.

Since the body only records black and white, colour won't help you here. Tone and separation will, so lean on the light. As the portraits guide says, light beats gear every time.

Written by Claude from this site's pages.