SMC Pentax K 85mm f/1.8
A compact telephoto with a large aperture is an extremely useful lens when combined with a nice compact body like the Pentax K-5, K-7, or even the old MX. How does the K 85mm f/1.8 work with a modern DSLR body?
Pentax has had 3 series of manual focus primes with a K mount. These are the K, M, and A series lenses. The K are lenses not otherwise marked M or A. The M series was the replacement to the K series, mainly making them smaller and cheaper to construct, and the A series added electrical contacts for the program cameras.
The SMC Pentax 85/1.8 is a very solidly constructed lens. It is compact for the aperture, and even at close focus remains fairly small The front element extends when you focus, but doesn’t rotate so filters maintain their orientation.
The lens is 6 groups with 6 elements. There is an 8 straight bladed diaphragm, and minimum focus is a very reasonable 0.85 m (2.75 ft) which is typical of lenses in this class. It has 52mm filter threads, and is fairly light at 331g given.
So how does this 85mm f/1.8 perform given that it is about 35 years old?