Rodenstock Apo-Sironar-S 150mm f/5.6

Lay a fine target flat across the whole 4x5 frame, stop down to f/22, and the corners drop into the same plane of focus as the center with almost no falloff. That edge-to-edge evenness, plus apochromatic correction that kills the green and magenta fringing you get on cheaper glass, is exactly what Rodenstock was chasing with the S line. The plain Apo-Sironar-N was already a strong plasmat. The S kept the formula but added ED glass for tighter correction, lower distortion, and a bit more coverage than the N.

It is a six-element symmetrical plasmat, the standard large-format design for a normal lens, and on the 150mm it covers roughly 231mm at f/22. That is generous for 4x5, with real room for front rise and shift, and it will technically cover 5x7 with very little movement left over. The 150mm focal length is the normal lens for 4x5, the rough equivalent of a 45mm on full frame, so this is the workhorse that lives on the camera when you are not reaching for wide or long.

Wide open at f/5.6 it is sharp in the center, but that aperture exists for focusing on the ground glass, not for shooting. You compose and focus bright, then stop to f/16 or f/22 where the whole frame is biting and diffraction has not yet softened things. Push past f/45 toward the f/64 minimum and diffraction starts eating fine detail, so the long end of the scale is there for depth of field when you have no other choice. Contrast is high and clean, flare is well controlled behind the multicoating, and the rendering is neutral rather than characterful. No signature swirl, no glow, just an honest record of what you pointed it at.

The honest limitation is that it asks for discipline and money. A clean 150 Apo-Sironar-S in a working Copal 0 still trades higher than the Apo-Sironar-N, the Nikkor-W 150, or the Fujinon-W that landscape shooters cross-shop against, and on most scenes you would struggle to see the difference between any of them in a print. The S earns its premium on flat subjects, repro and architecture and anything with detail running into the corners, more than on a misty hillside.

It is a landscape and studio standard, the lens that ends up on a field Linhof or a monorail as the default choice. The Copal 0 leaf shutter syncs flash at every speed up to 1/500, which matters under studio strobes, and the slow end runs to 1 second plus bulb for long exposures under the dark cloth. The 49mm filter thread is small enough that center filters and ND grads stay cheap. One metering habit worth keeping: when you rack the bellows out for tight portraits or anything near macro, your effective aperture drops and a meter reading at the subject lies to you. Feed the bellows draw into Zone Light Meter and let it compute the extension factor before you set the shutter, or your sheets come back a stop or two thin.