ground glass

Definition: Plate of glass used in focusing screens to capture a real image for focusing or viewing; also to diffuse light e.g. in viewers. * The surface is frosted, usually by acid etching or by grinding, to scatter light. * Used in large format cameras, usually with Fresnel field lens to even out rapid light fall-off away from the optical axis.
Don't write off glass
Instead, write on it. Despite being heavy, fragile, optically inefficient, glass has not been totally supplanted by plastics for large-format cameras. The reason is simply that you can write on it, stick tape and whatever you like -- each your lunch off it if you must -- and it will take it all and come out completely unscathed. Unlike any plastics.

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