The archive takes finished files in a short list of formats. We keep the master in the format the shop printed from. A manifest of SHA-256 hashes comes with every set, and the desk recomputes it on arrival before anything else is done. Files that arrive as JPEG are kept only as previews beside their master, never as the master itself.
Size is the main planning question for a set. A single A3 sheet at 600 ppi with four plates at 16 bits per channel is about 556 MB before compression. LZW brings a typical sheet down to between 180 and 240 MB, depending on how much of it is flat colour. A set of 1,200 such sheets therefore comes to between 216 and 288 GB, and the shelf plan uses that figure rather than the page count.
Shops that want to see one of these masters before they send a set can look at the sample masters, which include a TIFF scan and a PDF proof set at the sizes described here.
A 35 mm colour transparency scanned at 4000 ppi with 16 bits per channel is about 128 MB per frame. That is why a set of 4,300 frames, such as LC-0479, is listed at 540 GB and needs room for two copies of that size. Scanned frames compress less well than flat sheets, so the figure for a transparency set is usually close to its raw size.