In the long conversation between portability and image quality, Panasonic has offered a quiet but considered answer. The LUMIX S 20mm F2.5 — arriving in October at $849 — is a 142-gram full-frame lens designed for those who move through the world with intention, pairing an ultra-wide perspective with the optical engineering usually reserved for far bulkier glass. It is a small object built for large ambitions, whether those ambitions unfold on a city street, a mountain path, or a film set.