Réseau_plate
Réseau plate
Transparent camera lens attachment used to aid in scientific measurements
A Réseau plate is a transparent sheet of glass or plastic engraved with a grid of crosshatches called fiducial markers. It was commonly used in film cameras (before the advent of digital cameras) for scientific and technical photography. The plate is placed at the focal plane of the camera just in front of the film. When the frame is exposed the fiducial markers scatter incoming light, creating a permanent shadow on the negative.
The fiducial markers on a Réseau plate are sometimes called reticles. The Latin root of fiducial means trust, confidence; fiducial markers are trustworthy reference points. The Latin root of reticle means small meshwork bag, small net; a grid of reticles has a net-like appearance.