Ch. VII] PHOTOGRAPHING WITH THE MICROSCOPE 217 



bring different planes into view. He is in the habit of fixing his atten- 

 tion on the part of the field which is in focus and discarding the rest. 

 But in a photograph the part of the field not in focus appears in a 

 prominent way, which mars the beauty of the picture." 



Apparatus for Photo-micrography 



§ 340. Camera. — For the best results with the least expenditure 

 of time one of the cameras especially designed for photo-micrography 

 is desirable, but is not by any means indispensable for doing good 

 work. An ordinary photographic camera, expecially the kind known 

 as a copying camera, will enable one to get good results, but the trouble 

 is increased, and the difficulties are so great at best that one would 

 do well to avoid as many as possible and have as good an outfit as 

 can be afforded (fig. 129). 



The first thing to do is to test the camera for the coincidence of 

 the plane occupied by the sensitive plate and the ground-glass or 

 focusing screen. Cameras even from the best makers are not always 

 correctly adjusted. 



For the method of procedure see above, § 334. 



The majority of photo-micrographs do not exceed 8 centimeters 

 in diameter and are made on plates 8X11, 10X13, or 13X18 centi- 

 meters (3IX4I in., 4x5 in., or 5x7 in.). 



For pictures larger than these it is best to make small, very sharp 

 negatives of moderate enlargement and then print these at any 

 desired size by means of projection apparatus (see under enlargements, 



§ 359)- 



§ 341. Work Room. — It is almost self-evident that the camera 



must be in some place free from vibration. A basement room where 

 the camera table may rest directly on the cement floor or on a pier 

 is excellent. Such a place is almost necessary for the best work with 

 high powers. For those living in cities, a time must also be chosen 

 when there are no heavy vehicles moving in the streets. For less 

 difficult work an ordinary room in a quiet part of the house or labora- 

 tory building will suffice. It helps much to have rubber corks in 

 the lower ends of the table legs. The legs may also be made to 

 stand on four thick pads of rubber or of thick woolen cloth. 



