I have a Zeiss Ikonta 6x9 folder acquired for a pocketable shooter for casual hiking. The shutter seized up so I opened it up to give it a clean and lube. That was successful, and I noticed the Tessar lens accomplished its focusing with a front element that moved while another element behind it was stationary. Makes me think this thing focuses like the human eye by changing the focal length rather than changing the lens to film distance. Anybody know the story on this?