1902 Re CO rd Photography 225 



great, and a "hard" picture, in which sunhghted parts look 

 as if snow has been falHng, results. 



In other words, the contrast between the tones is regu- 

 lated by the length of development. The best and simplest 

 plan is, in my opinion, to keep to one formula of developer, 

 and to develop for such a time that a contrast between 

 the tones results correctly representing the natural subject. 

 In winter this time is much longer than in summer, and 

 it also varies with accidental variations in the developing 

 solution. 



I discovered that an observation of the time of appearance 

 of the image on the plate gives an exact measure of the 

 activity of the developer and enables the desired contrast 

 in the negative to be secured by timing alone. 



Let me give practical details. Nothing better than a 

 pyro-soda developer can be used, and I will presume that 

 a well-known formula — that given for Ilford plates — is 

 followed, the smaller amount of pyro mentioned in the 

 formula being used. If with this developer the time of 

 appearance of the image is noted and the plate left in for 

 a total of 5I times this time, a negative of standard contrast 

 will be secured at any time of the year. 



The procedure is as follows : Having plate and developer 

 ready, take out your watch, and when the hand touches an 

 even minute pour on the developer. Begin at once to count 

 seconds and note the number at the first appearance (watch- 

 ing closely) of any trace of image on the creamy surface. 

 This number of seconds is the time of appearance, and 5!^ 

 times the appearance is the total time to develop. Thus, 

 the image appears in 30 seconds, and it must be developed 

 for 165 seconds or 2f minutes from the moment of pouring 

 on the developer. The 5I times is called the multiplying 

 factor, and expresses the choice of the photographer in the 

 contrast required in the print. If for a special subject an 

 extra amount of contrast is required in the print, a larger 

 factor (longer development) must be used, and a shorter 

 factor if the contrast in the subject is required to be sub- 

 dued. Different developers and different formulas require 

 different factors, but the factor does not require altering for 

 •different makes of plate. 



