NEGATIVE MAKING 89 



tory radiants, the main point consisting in 

 securing even illumination. This accom- 

 plished, the section of camera carrying the 

 lens is pushed forward nearly to the front and 

 fastened. Then the rear section is to be 

 moved forward or backward until the object 

 is seen in focus on the ground-glass screen. 

 If smaller than is desired, the lens must be 

 moved a little nearer to the object and the rear 

 section of camera farther from it; if too 

 large these movements must be reversed and 

 the operations continued until an image of 

 required dimensions is projected on the screen 

 and the final sharp focusing effected by gently 

 moving the screen section backward or for- 

 ward, as becomes necessary. The object glass 

 or lens is not to be moved for this purpose, 

 as with a microscope. It is effected entirely 

 by the focusing screen. Rectilinear lenses of 

 3 to 5 inches focus, as usually furnished with 

 the smaller cameras, are the best for photo- 

 macrography in general, but those of longer 

 foci may be used if the bellows have sufficient 

 extension. The focusing should be done with 

 full opening of the lens, c ;but exposures made 

 with stops of //22 or 7/32. 



Should we not have a camera embracing the 

 features of the E. R. & C., some method 



