The oldest lens I tested adapted on an EOS R6 Mark II was the old EF 70-210mm F/4 Arc Form Drive lens from 1987. Everything with the lens did work but the camera functioned in a degraded manner. Most features of the camera were unavailable. The 4 fps limit was even still in place that all Arc Form Drive lenses have.
-Demetrius
Bodies: EOS 40D & EOS 5D Mark IV
Lenses: EF Holy Trinity, EF 50mm F/1.8 STM, EF 70-210mm F/4 & EF 85mm F/1.8 USM
Speedlites: 420EX, 470EX-AI, 550EX & 600EX II-RT
