Lenses Used in Tests
I purchased both the EF 50mm f/1.4 USM and EF 50mm f/1.8 II lenses new. The f/1.4 lens had been used for 4 years. I purchased the EF 50mm f/1.0L USM lens to evaluate it for use in gymnastics photography. It was in 9.5 out of 10 cosmetic condition. However, I had to return it to the seller for refund when it demonstrated consistent front-focusing characteristics in ambient light (e.g., modeling lights from monolight studio flashes). The lens appeared to function normally in low light when manually focused through a 2.5x finder. However, the possibility must be considered that EF 50mm 1.0L USM lens used in these tests performed suboptimally in other areas (e.g., resolution and 50% MTF.)