The Pentax FI-40 Focusing Screen is an interchangeable focusing screen compatible with SF-series cameras.
Three screens were available in addition to the standard one: FD-41 (Scale matte Screen for Photomicrography and macrophotography), FG-40 (AF sensor field surrounded by a grid) and FI-40 (AF sensor with a horizontal and a vertical millimeter scale). Both screens are well suited to scientific, architectural, and macrophotographic work.