CHAPTER XVIII 



INTENSIFICATION AND REDUCTION 



By Beverly Dudley 



The ideal situation to be striven for in the technique of the photographic process is 

 to produce negatives and prints that are free from blemishes and in which the opacities 

 of a portion of the image are properly related to the visual brightness of the corre- 

 sponding areas of the original subject. When the negative or print departs from 

 these ideal — or other desired — conditions, corrective processes maj' sometimes be 

 employed to advantage. Among the most important corrective processes may be 

 listed intensification and reduction which are chemical in their characteristics. 

 Physical or mechanical corrective processes, such as retouching, spotting, and the 

 various control methods which may be used in printing will not be discussed in this 

 chapter. The chemical corrective processes may be applied either to the negative or 

 to the print. Usually, however, it is more satisfactory to make a new print than to 

 attempt to correct for certain defects, so that intensification and reduction are used on 

 prints relatively infrequently. Consequently, the majority of the material in this 

 chapter refers primarily to intensification and reduction of negative materials. 



INTENSIFICATION 



Intensification is the photographic process by which the density and contrast of the 

 silver image are increased. Intensification may be necessary or advisable for several 

 reasons: (1) The negative may be underexposed and so thin that the printing time to 

 obtain the desired result may be inconveniently short. (2) The negative may be 

 underdeveloped and therefore lacking in contrast, in which case intensification may be 

 used to increase contrast. (3) Portions of the negative may be so thin that the 

 resultant print is dark and lacking in detail. In this last case, local intensification of 

 the negative may be quite helpful. 



In a negative, intensification may be effected by any chemical or dye process which 

 decreases the transmission of light through the negative. Because such light- 

 absorbing substances may not be neutral, i.e., gray, in color and because the sensi- 

 tivity characteristics of the human eye differ from those of the photographic paper 

 upon which the negative is to be printed, the visual effect of intensification may differ 

 from the photographic effect. Consequently, it is not always possible to determine 

 the degree of photographic intensification from visual examination or measurements 

 made on an intensified negative. In positive prints, intensification may be effected 

 by any chemical process which increases the visual density of the deposit of silver on 

 the paper, but where prints are concerned, it is highly desirable that the intensification 

 produce a neutral rather than a colored effect. 



Classification of Intensifiers. — Intensifiers may be classified according to the three 

 common methods by which intensification may be accomplished: 



1. A new film or deposit of silver may be added to that already existing on the 

 negative or print. The silver intensifiers are the only ones producing intensification 

 of neutral color. They have the further advantage in producing a permanent effect. 



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