File:The American annual of photography (1922) (14801447113).jpg

Identifier: americanannualof36newy (find matches)
Title: The American annual of photography
Year: 1922 (1920s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
may be considered safe, it will be found advisable to test theone in use before exposing any plates to its rays. A simpleyet effective test is to expose say half of an ordinary plateto the light coming from the lamp. This is done while theother half of the plate is held between the leaves of a book.If upon development the plate shows no darkening in theportion which was exposed to the ruby light, the lamp maybe considered safe; if on the other hand a dark area appearsupon development, it will be a sure indication of the fact thatthe ruby lamp should by no means be regarded as a safeilluminant of the dark-room, but should be made so. Theintroduction of a few sheets of orange or ruby fabric will asa rule remedy this evil, and render the lamp quite safe. As already stated the most universally adopted method ofexposure for plates or films—(the latter having been placedupon the market quite recently) is to have them in doubleenvelopes of red and black light proof material. This method 80
Text Appearing After Image:
o 1-4 WO w < WH 8i proved a rather serious handicap especially when exposures ofexceedingly short duration were required.* Such exposureswhen made were as a rule hopelessly undertimed and prac-tically rendered valueless for diagnosis. In order to overcomethis decidedly serious drawback intensifying screens areemployed. These screens may be composed of differentchemical constituents such as zinc sulphide, calcium tungstateor platinocyanide of potash, mounted in an aluminum frameor cassette very much resembling the ordinary printing frame.The X-Ray plate after having been carefully dusted is placedin the dark-room, into this cassette, emulsion side in contactwith the screen. The cassette is then closed and is readyfor exposure. In order to take the radiograph the cassettecontaining the plate is placed in apposition to the patient insuch a way that the ray will pass through the glass side ofthe plate to the screen, the latter becoming fluorescent inten-sifies the plate and permits of

Note About Images