CHAPTER XII 



SOME PROGRESSIVE EXAMPLES 



HOWEVER full any general instructions may be in photo- 

 micrographic work, they cannot possibly cover the whole 

 of the varied conditions and circumstances that may arise. 

 It may, therefore, happen that a series of progressive examples, 

 in which various types of objects are selected and various 

 methods of photographing them are described, may prove 

 more useful in particular cases than a treatment of the subject 

 on a broader basis. 



All the photographs in Plates I to X are selected not merely 

 as pictorial examples, but as types and varieties that may 

 easily arise in the course of practice. They do not claim to 

 be of necessity the finest that can be produced of a particular 

 subject, but in all cases they are fair examples of what may 

 be expected from an object of average quality. It is a matter of 

 common knowledge that many extremely fine examples of photo- 

 micrographic work have been produced not merely as the result 

 of perfect technique, but in large part because the object itself 

 happened to be of unusual quality and suitability. All those 

 here delineated have been specimens of average quality, and 

 such as any ordinary worker may expect to meet with in the 

 usual course. 



The description given is generally sufficient to indicate the 

 exact procedure. The only factor that may require variation 

 to obtain the same result is camera-length. It has already 

 been stated that lenses, even of the same nominal focal length, 

 vary within moderate limits in magnifying power. This may 

 be allowed for, and any necessary correction made by variation 

 of the camera-length. Therefore, in some cases where an 

 achromatic objective has been used in which the focal length 



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