I went to an art exhibit this weekend where they had many digital prints made from what they said were original glass plate negatives shot during the 1930 discovery/robbing of King Tut's tomb. I don't know anything about glass plate negatives, but I had assumed that into the 1930s, they would be using nitro film. During what time period was silver-gelatin-on-glass in widespread use for commercial photography? When did film start to take over? I imagine that glass negatives can be printed just like film negatives, probably even easier because they are flat. But are there any other differences in technique compared to film? I suppose you need a special camera for glass as opposed to film negatives.