Pentax 75-150 mm M f4 versus Sony 55-210 at f8
Pentax 200 mm M f4 versus Sony 55-210
The Pentax lenses are sharper in the corners and don't suffer from a warm colour cast, but the Sony provides a similar level of sharpness in the centre of the frame and is less prone to chromatic aberration.
The file sizes of the JPGs produced by PS from TIFFs resulting from a Lightroom raw conversion are as follows: -
Pentax 75-150 13913
Sony 55-210 13179
Pentax 200 12721
Sony 55-210 12037
Suggesting that both Pentax lenses are collecting more data.
Edit - since writing this I have discovered that my Pentax 200 mm f4 lens is not focusing to infinity. Once I get this sorted I'll do another comparison. 16-8-2015