I've recently bought the Pentax SMC-M 50mm F1.7 lens from a forumer. But the photos were not quite sharp at F1.7. It turns out better at F4 or smaller. I dont know if its the lens issue or my settings. can anyone advise?
F4
IMGP0335 by Li Shixian, on Flickr
F1.7
IMGP0334 by Li Shixian, on Flickr
F4
IMGP0335 by Li Shixian, on Flickr
F1.7
IMGP0334 by Li Shixian, on Flickr