ON PHOTO-MICROGRAPHY. 197 



exposure, are measured out and added to the 

 contents of the beaker, which are then to be 

 returned to the plate after the water has been 

 poured off. This will retard the development and 

 preserve the purity of the shadows, while the high 

 lights gain in density. After a time 30 or 40 drops 

 of B may be added to complete the development. 

 Under-exposure is indicated by slowness in the 

 appearance of detail in the shadows and half tones 

 after the full quantity of B has been added, and is 

 remedied by the addition of 10 to 20 drops of D to 

 the developer. In all cases when additions have to 

 be made to the developer, the additional substance 

 should be poured into the beaker, and the solution 

 from the plate added to it. This will secure a 

 uniform mixture before the developer is returned to 

 the plate. If the additions were simply poured 

 directly into the tray they would act locally and 

 spoil the picture. The operator must learn to 

 recognise an under- or an over-exposed plate by its 

 character after development as well as before. 

 Over-exposure results in thin (i.e., weak or trans- 

 parent), flat, soft negatives, full of detail, but 

 deficient in intensity, while an under-exposed and 

 forced plate yields a dense and harsh negative with 

 little detail. It is useful to know this, because one 

 may occasionally wish to give the negative a soft or 

 a harsh character to suit some special subject. The 

 rule is, for violent contrasts, under-expose and 

 force in development ; for a finely-graduated image 

 over-expose, and use the bromide freely. For most 

 purposes we should avoid either extreme. 



If the films have a tendency to frill (i.e., to 

 pucker and leave the glass at the edges) or blister 



