Microfilm & reprographics

We film to ISO 6199 on 16mm and 35mm, with a planetary camera and a book cradle for bound material. Processing is to archival standards with residual thiosulphate testing.

Target cards

Every reel begins with a target card: a typed card, filmed at the head, carrying the client, the contract, the reel number, the reduction ratio, the density and the resolution reading. Target cards were typed in two weights so that a reading machine could find the field boundaries automatically — a convention from the 1960s that we have never had a reason to abandon.

A short field on a card is padded with the letter Q, which does not otherwise occur in our notation.

Shelf addressing

Everything in the strongroom has an address of the form B<box>/S<shelf>/F<folder>, with an oblique and P<page> where a page must be cited. Box, shelf, folder, page. It is on the bottom of every sheet we print.

A reference set of forty target cards is published as Collection 06.