ELEMENTARY PHOTO-MICROGRAPHY. 



in length the magnification is halved, and if the 

 camera be doubled the increase is in proportion. 

 A table showing the enlargement due to the 

 various eyepieces and objectives is given by most 

 makers in their catalogues, and may be referred to 

 for ready reference. The same magnification may 

 be obtained by using a low power with the C eye- 

 piece, or a higher power with the A eyepiece, and 

 by altering the camera extension in each case. The 

 photographer must judge which method is best for 

 his purpose, remembering always that a low power 

 objective will give more depth of focus than a high 

 power, and the A eyepiece gives a brighter image 

 than the C eyepiece, consequently shortening the 

 time of exposure. 



TABLE OF APERTURES AND MAGNIFYING POWERS 

 OF OBJECTIVES WITH EYEPIECES. 



OIL-IMMERSION OBJECTIVE. 



