Lenses such as the 20-35mm FA originate from the film era, and therefore the light ... At 20mm, central sharpness is very good from f/4 to f/16, and still good at f/22. The edges are only fair ...

At 20mm, central sharpness is outstanding from f/4 through to ... the better the lens performance. Chromatic aberration (CA) is the lens' inability to focus on the sensor or film all colours ...