In the early days of biological electron microscopy (the 1950s and 1960s), projection slides of electron micrographs for talks or teaching were generally prepared as 3-1/2″ X 4″ lantern slides, which were shown using large lantern-slide projectors. It was felt by professional electron microscopists that the detail, tones, and general image quality of electron micrographs could be adequately portrayed only in this larger format.

However the large lantern slides were very cumbersome, and most professionals began switching to 2″ X 2″ slides in the early 1970s. Some of us during that period put in a great deal of time trying to work out a procedure for printing EM negatives directly on 2″ X 2″ glass Kodak Projector Slide Plates, following the general approach by which we had previously made the 3-1/4″ X 4″ lantern slides.