The Canon EF 135mm f/2L USM is one of the most respected telephoto primes ever made and one of the few legacy lenses where the secondary market price has declined meaningfully as photographers have migrated to mirrorless systems and RF glass. Used copies trade in the $600–$750 range — less than they commanded five years ago, and substantially less than the optical quality warrants. The Sigma MC-11 adapter, which communicates the EF protocol to Sony E-mount bodies with high fidelity, adds approximately $199.