Gelatin dry plate negatives, as opposed to the earlier
wet collection glass negatives, were commercially produced, by companies
such as The Imperial Dry Plate Company of London, on thin glass
plates coated with light-sensitive silver salts gelatin. This process
was in common use by photographers from the late 1880s into the early
1920s, when film replaced glass. Most prints from glass plate negatives were made using the contact print method. And
prints, the size of the negative determined the size of the photograph.
The larger the negative, the larger the print.