Originally posted by BATMON What's the DA 4-5.8 55-300mm ED WR "Sweet Spot"?
It depends what focal length you use, and whether centre sharpness or edge sharpness is the priority.
See this test of the pre-WR version (optically identical, except for the improved coatings on the later version):
Pentax SMC DA 55-300mm f/4-5.8 ED - Review / Test Report
On this test, f8 gave the best centre sharpness at each tested point up to 300mm, when it was shaded by f11. For more even resolution across the frame at the wide end (say 55-100mm), f11 was better, at the cost of a little centre sharpness.
Tests like this aren't gospel (it's just one sample after all) but they give a general indication. As a general rule consumer zooms like this always do better stopped down a bit. With the DA-L version I generally try to stop down one or two stops, unless I want the wider aperture for more light or shorter DOF. At 300mm I try to use f8 (or up to f11) if the light is good enough. But f7.1 is OK too.
Last edited by Des; 04-10-2017 at 07:40 PM.