If you want programmable high-resolution knobs, this is an area that the music industry has had covered quite well for a long time. A quick Googling for "midi controller knob" brings up:

Livid Alias 8

Livid DS 1

Nektar Panorama P1

MIDI Fighter Twister

Behringer B-Control Rotary BCR2000

Akai LPD8

The last one is about seventy bucks and gives you eight independent knobs and eight pads.

Of course, there's value in minimalism and a good UX for configuring/programming the knob(s), but there's also something to be said for just trying to solve the problem yourself based on what's currently available. If a $70 MIDI controller makes your Photoshop experience noticeably better, great. If not, a single knob might not end up being worth it either, regardless of how well-made it is.