The plate having become sufficiently coated is taken from the bath,
well drained, and placed in the holder or shield, and a piece of
glass of the same size put behind it, which is to receive the
pressure of the spring on the door of the holder, and force the
plate into its proper position evenly, so that all parts will be in
focus.
The holder containing the plate is then taken to the studio, or
light room, where the subject, we will say, has already been posed;
the camera set and focused, the exposure is then made, after which
it is returned to the dark room for development.