Bronica's 6x6 short-tele portrait lens — the leaf-shutter Zenzanon-S 105mm f/3.5 for the SQ.
The Bronica Zenzanon-S 105mm f/3.5 is a short-telephoto lens for the Bronica SQ 6x6 medium-format system, from the early SQ era around 1980. The S designation marks the earlier generation of SQ Zenzanon optics that preceded the later PS lenses. On the square 6x6 frame a 105mm sits in the short-tele range favoured for portraits.
This manual-focus lens mounts on the Bronica SQ leaf-shutter bayonet, with a focal length of 105mm and a maximum aperture of f/3.5. It uses the in-lens Seiko leaf shutter common to the SQ system, giving flash synchronisation at all shutter speeds. Element count, weight and filter size are omitted here rather than stated without confirmation from the sources used.
A 105mm on 6x6 gives a comfortable working distance and a flattering perspective for head-and-shoulders portraits. The moderate telephoto compresses the background gently and, with the larger negative, renders smooth out-of-focus areas. It also serves for tighter general framing and detail shots where the normal lens is too wide.
On the used market the S 105mm is a common and affordable SQ lens. Check the leaf shutter for even firing at all speeds and listen for sluggish slow speeds that indicate old lubricant. Inspect the elements for haze, fungus and separation, confirm the aperture blades are dry and snappy, and verify the coupling to the SQ body and film back works correctly.