My early forays with the Pentax SMC-M 135mm f/3.5 yielded the above. Looks a bit soft and, to me, it seems to struggle a lot more with darker conditions than I was anticipating, but copes nicely enough with bright ones (except at wide-open, it seems). Believe the above to be around f/4 and the below to be approximately f/5.6. The below is a bit busy, but highlights a bit better how it starts crisping up around f/5.6. It renders colours beautifully, when caught just right. Love the purple in the above.