half-tone

a. Having, consisting of, or pertaining to, half tones; specif. (Photo-engraving), pertaining to or designating plates, processes, or the pictures made by them, in which gradation of tone in the photograph is reproduced by a graduated system of dotted and checkered spots, usually nearly invisible to the unaided eye, produced by the interposition between the camera and the object of a screen. The name alludes to the fact that this process was the first that was practically successful in reproducing the half tones of the photograph. [ Webster 1913 Suppl. ]