Bronica's 6x6 wide — the leaf-shutter Zenzanon-S 40mm f/4 for the SQ system.
The Bronica Zenzanon-S 40mm f/4 is a wide-angle lens for the Bronica SQ 6x6 medium-format system, introduced when the SQ line launched around 1980. The S designation marks the earlier generation of SQ Zenzanon optics that preceded the later PS lenses. On the square 6x6 frame the 40mm gives a wide field of view for scenic and architectural subjects.
This is a manual-focus lens for the Bronica SQ leaf-shutter mount, with a focal length of 40mm and a maximum aperture of f/4. It carries the in-lens Seiko leaf shutter used across the SQ system, allowing flash synchronisation at all shutter speeds. Element count, weight and filter thread are omitted here rather than presented without confirmation from the sources consulted.
A 40mm on 6x6 covers a wide angle of view suited to landscapes, architecture and interiors, with the balanced composition the square format encourages. Stopping down extends depth of field across the frame for scenic and building work, and the larger negative renders smooth tonal gradation. The leaf shutter also permits fill-flash at any speed outdoors.
On the used market the S-series 40mm is less common than the standard lenses and sits below the later PS versions in price. Check the leaf shutter fires evenly at slow and fast speeds, inspect the glass for haze, fungus and separation, and confirm the aperture blades are dry and responsive. Verify the mount couples cleanly to the SQ body and film back.