ABSTRACT
The printing characteristics of a black and white negative consisting of silver particles are largely determined by the optical density range, the spectral transmission characteristics relative to the spectral sensitivity of the print material, the spectral power distribution of the illuminant, and the nature of the printer illumination. Various types of illuminant are used in printing systems, being chosen for their size, actinic light output and spectral power distribution. Projection printing using a condenser system to illuminate the negative is a traditional and effective method. A hand-operated enlarger has too low a rate of print production to be economical for photo-finishing laboratories. The projection printer or optical printer consists essentially of a projector through which the negative runs, and a synchronous camera containing the ‘raw’ or unexposed print ‘stock’. Digital technology and scanning systems for both negative assessment and print exposure are used in high speed printing in both minilabs and commercial laboratories.
