I own a 135mm SM Super Takumar F3.5 (49 filters) that is a great performer and quite small. Resolution is really nice across most of the aperture range with slightly low contrast. At times I have read some threads praising the SMC F2.5 58mm filter models and the K mounts as well. Does anyone have practical experience between the screwmount F3.5's and the others? While I appreciate what I have, I wouldn't mind acquiring another for certain subject matter if it had better performance .