The instructions read like a warning. To turn a Canon FD 85mm f/1.2L into a cinema lens, you remove the rear glass element by hand, a step one modding company calls risky enough that they sell you a replacement element just in case you crack the original. The mount comes off. A follow-focus gear goes on. The aperture ring, which used to click firmly at every stop, gets filed smooth so it can be pulled through in one motion during a shot. None of it can be undone.
None of this is what the lens was for. Canon introduced it in the early 1970s as part of a trio of FD lenses, at 24mm, 55mm and 85mm, built around a technology that was then genuinely hard to manufacture: aspherical elements ground to correct aberrations no spherical lens could touch. At release, it was the brightest 85mm SLR lens anyone had made. When Canon revised the line for the New FD mount, this lens earned the red ring reserved for its L-series professional glass, and it was popular enough that when the autofocus EF mount finally arrived, Canon adapted the 50mm and 85mm f/1.2 designs onto the new system rather than let them die with FD.
Die is roughly what FD did anyway. In 1987 Canon dropped the mechanical FD mount entirely and moved to the fully electronic EF mount to chase autofocus, a switch so complete that the two systems share no compatibility at all. For a still photographer, that should have been the end of the story: a beautifully made manual lens stranded on a dead mount, the kind of thing that ends up in a drawer.
It didn't end up in a drawer. It ended up on film sets, because it turns out the qualities that made it a good portrait lens, an aperture ring you can feel, a mechanical build that survives decades, a rendering people describe as soft and glassy at f/1.2, are also qualities cinematographers want and can no longer easily buy. Canon's actual cinema lenses from that era, the K35 set, now sell for prices most working filmmakers can't justify. The FD 85mm f/1.2L, and its siblings, became the workaround. A company called Simmod, founded by a working cinematographer, built a business specifically around converting this one lens to EF mount for cine rigs. Other shops, like Couto Camera, offer the same service as a menu item: declick the aperture, swap the mount, add the gear.
None of this happened because someone rediscovered the lens for the job it was built for. A forum thread from a few years back tracks the effect on price: copies going for around $500 to $600 in 2017 were closing at several thousand dollars by 2022, and the poster's own theory was straightforward, filmmakers buying up still lenses as a cheaper stand-in for cinema glass that costs six figures as a set.
So there are now two versions of this lens circulating. One still has its breech-lock mount, its clicked aperture ring, its original rear element, exactly as Canon built it for someone metering a portrait by hand. The other has had its back cut open and rebuilt to do a job it was never designed for, and can't be put back the way it was. Buy the one at Glazer's, and you're choosing which future it gets.