I had an FA 80-320 mm that gave good results with my K5 but was abysmal on the K3. The lens just quit and died a few weeks ago (I had paid 115 $ for it so repair is out of the question). Instead I got a second-hand
DA 55-300 mm f/4-5.8 HD on eBay from Japan for a good price and in like-new condition. I tried it on a K20 that had been mothballed for a few years and it performed admirably well (first image, 300 mm @ f/11). Last week I mounted the HD lens on my K3 and, lo and behold, it keeps performing admirably well even on a 24 Mpx sensor (second image : 90 mm @ f/11). Just my 2 cents.
Last edited by RICHARD L.; 05-08-2020 at 12:24 PM.