Bronica / Nikkor Zenzanon-PG 100mm f/3.5

On a 6x7 negative, 100mm sits right at normal. The crop factor runs about half, so this lands near a 50mm on full frame, which means the perspective comes out flat and unforced. Nothing stretches at the edges, nothing telescopes in the middle. That is the whole appeal of the focal length on this format, and it is why the 100mm f/3.5 PG ended up as the default portrait and product lens for studios that ran 120 through the 1980s and into the 90s.

Skip the old myth that the PG glass is rebadged Nikkor. Nippon Kogaku did supply lenses for the early focal-plane Bronicas, the S and S2 bodies, but that arrangement was long dead by the time the GS-1 arrived in 1983. The PG line was Bronica's own work, designed in-house with computer-aided optical layout and multi-coating, built specifically for this system. The 100mm was one of the lenses available from the start, part of a single unified design family rather than anything carried over from the focal-plane era.

What it renders is clinical in the best sense. High microcontrast, a flat field that holds sharp corners by f/8, and enough resolution to copy artwork or read a face without flattering either. Wide open at f/3.5 the center is already crisp with a soft falloff toward the corners. The out-of-focus areas are smooth and largely characterless, no swirl, no painterly drama. On 6x7 you do not need the lens to separate the subject because the format already does it, so the straight, honest drawing works in its favor. Flare resistance is decent but not absolute. The front element is broad behind the 72mm thread, and a hard backlit source will lift contrast if you shoot without the hood, so keep it mounted.

The leaf shutter is the system's whole argument, and the 100mm carries it in the barrel rather than the body. That buys flash sync at every speed to 1/500, which matters enormously for strobe work on location. You can pull a bright ambient sky down with a fast shutter while your fill flash stays balanced, something no focal-plane medium format back will do. In Zone Light Meter, set the leaf-shutter speed range when you meter for fill, since balancing strobe against daylight keeps you working the top of the dial rather than the long exposures a focal-plane body would force.

The honest drawback is the shutter itself. Leaf shutters are mechanical assemblies that drift with age, and a GS-1 lens with a sticky or inaccurate one can cost more to service than a clean body. Buy a copy that has had a recent CLA, or budget for one. Speed is the other limit. f/3.5 is slow by 35mm standards, so this lives on a tripod with strobe far more than it works handheld in dim rooms.

The GS-1 trades cheap against the Mamiya RZ67 and the Pentax 67, the two bodies most 6x7 shooters weigh it against. The Bronica is the lightest and most compact of the three, and the 100mm PG is the lens that justifies the choice. People still pick this combo because it puts genuinely sharp optics and any-speed flash sync on 6x7 for far less than a digital back, and a serviced copy keeps shooting for decades.