Lens board

[1] The lens board itself is usually flat, square, and made of metal (most commonly aluminum), wood, or plastic.

The overall size and shape of the lens board depends on the brand of camera and film format used.

The rear surface of a lens board is usually painted matte black to keep light entering the camera through the lens during exposure from reflecting off the surface and interfering with the projected image.

While most lens boards are flat, some are recessed to accommodate wider focal length lenses which must be positioned closer to the film plane.

A recessed lens board effectively reduces the flange focal distance of a camera.