I guess it's only natrual to compare what you have on hand. Since I have 7 lenses in the 135mm focal length, I have decided to see what the differences between them are. All lenses are compared against one of the sharpest lenses Canon has ever made, the EF 135mm F2L. It's clear that none of the lenses tested are better than the 135mm F2L, at any focal length, but none of them are bad, even wide open, except the Chinon, which is a little soft, has CA and has low contrast at F2.8. The surprise is one of the Pentax S-M-C 135mm F2.5 lenses. Reasonably sharp at F2.5 and comparable sharpness at F5.6 and F8 with the Canon, but not as contrasty.