You searched for: “calibration plate
calibration plate (s) (noun), calibration plates (pl)
A glass negative that has been exposed with its emulsion side in the same position as that which is presented by the service emulsion at the time of exposure, providing a record of the distance between the camera's fiducial marks or references for comparisons or measurements.
This entry is located in the following unit: calibra-, calibr-, caliber- (page 1)