PRINTING PROCESSES 



415 



These effects may be summarized as follows: 



Table I. — Print Characteristics 



Tone and Exposure Range. — Printing papers have two general characteristics. 

 One is opacity (or density) or tone range; the other is exposure range. By tone range 

 is meant the ratio of the light reflected from the brightest high light of the paper 

 to the light reflected by the deepest shadow. All papers will print black if exposed 

 long enough. All reflect white light if unexposed and if the base is un tinted. The 

 texture of the surface has a marked effect upon the tone range. A matte surface will 

 reflect more Hght from a black portion of the picture than will a glossy paper. There- 

 fore the black of a matte print will not be so black as that of a glossy print. 



The exposure range is the ratio between the exposure required to give the deepest 

 black and the exposure required to give a silver deposit which is just perceptible. The 

 exposure range is usually much less than the opacity range of negative materials. 



A contrast paper may have an exposure range of 5 to 1 ; a soft paper may have an 

 exposure range as great as 50 to 1. Papers or other degrees of contrast will have 

 exposure ranges between these values. With this degree of contrast control available 

 by selecting the most suitable paper, the photographer can make prints having accu- 

 rate tone reproduction from negatives having opacity ranges of 5 to 1 (density range of 

 0.7) up to 50 to 1 (density range of 1.7). ^ 



The photographer who aims at prints for salons will choose meticulously the 

 paper which has the tone and exposure range necessary to show what he considers 

 will get favorable attention from the salon judges. For truest reproduction, a paper 

 of proper exposure range must be chosen to be used with a given negative. But 

 prize-winning results are often attained by deliberately (or accidentally) disregarding 

 this rule. 



If the photographer makes a single kind of negative, portraits for instance, under 

 accurately controlled conditions of exposure and development, he will need to use but 

 a single grade of printing paper. The amateur and the commercial finisher, however, 

 must have at hand several grades of paper, some hard and some soft, because they must 

 print from negatives made under all sorts of conditions, and often processed under 

 conditions which may produce opacity ratios which are not like the subject brightness 

 ratios. Most photographers compromise by using a normal or medium grade for most 

 work and sacrificing some accurateness in printing negatives which are not exactly 

 suited to these grades. Harder or softer papers are used for these negatives which 

 are patently out of the normal or average class. 



1 With carbon and platinum processes much longer exposure scales are possible, platinum making 

 possible a range of 100 to 1. 



