Skilled photographers can examine a negative and can interpret its renderings with practically as much satisfaction as they get from a print, whereby a considerable amount of time can be saved in an emergency. The original glass negative should always be used when accurate measurements are to be made. These and a few other cases constitute the only use of a negative apart from its normal one, namely, for producing positive prints, usually in large numbers. The commonest form of print is on paper, although the most satisfactory print from the photographic standpoint is the transparency on glass or celluloid film.