When I switched to mirrorless in 2012 I chose the micro 4/3 system with the Panasonic GH2. On of the most offered lens of the system was the Panasonic 20mm F1.7. Although it had some shortcomings like the noisy and slow autofocus motor you could hardly complain about its image quality. It was sharp straight from F1.7, one of the best amongst the micro 4/3 lens. I used this lens a lot on photo walks and holidays. This was the point when I fell in love with the equivalent 40mm focal length.