MICROSCOPE AND CAMERA ALLIED 



meters, may appear puzzling but really it is quite 

 simple. Suppose we wish to make a photo-micro- 

 graph of a penny stamp and we wish it to be 

 magnified ten diameters, we should require a large 

 camera for the operation, but that, for the moment, 

 is beside the point. Our penny stamp, magnified 

 ten diameters, would be equal in area to ten 

 horizontal rows of stamps, each row containing ten 

 stamps or, in other words, it would occupy the 

 same area as one hundred penny stamps. 



To find the magnification possible with our 

 camera and lens, extend the camera bellows to the 

 full and set up a foot rule in front of the lens. 

 Move the camera from a distance slowly towards 

 the rule till it is sharply focussed, then carefully 

 measure the distance between the inch lines on the 

 focussing screen; if the lines are three inches apart 

 we shall be able to make photo-micrographs three 

 times the size of our object and we shall probably 

 desire something better. 



To obtain a considerably magnified picture we 

 must have a lens of short focal length and a 

 camera with long bellows, in fact in theory the 

 amount of magnification is only limited by the 

 length of the bellows, so that an extraordinarily 

 long camera should give us a much magnified 

 picture. We cannot lengthen our bellows without 

 considerable expense, but we can shorten the focal 

 length of our lens. If we obtain, at the cost of 

 a few pence, a convex lens of short focal length, 

 such as is used in cheap magnifiers we can easily 



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