As I promised about a month ago, the new firmware supports all Contax 645 lenses' AF on GFX50s is ready for download. Compare to firmware v2.1, 45-90/4.5 and 350/4 has been added to the AF list. Fringer C645-GFX adapter users, please visit https://www.fringeradapter.com/#service-and-resources to download new firmware, i.e. version 2.21, and upgrade your adapter according to the steps described in user's manual. Or you can order a new adapter installed with the new firmware from https://www.fringeradapter.com/#buy-it-now .
Due to the design of the old lenses, their AF performance on GFX50s has limitations. Don't expect them perform like native G lenses on GFX50s or C645 lenses on C645 camera body. That would not be changed until new G mount camera introduces PDAF. Let's pray that Sony would hand over medium frame CMOS equipped with latest technology sooner.
AF demo video