TECHNICOLOR AND OTHER METHODS 203 



the speed factor of the film, it takes only an instant 

 to find the amount of time required to get the cor- 

 rect exposure from the readings on its face. 



So that greatest of all troubles safely overcome, 

 the other steps, focus, lighting, magnification in the 

 microscope, preparation of the subject, etc., correctly 

 done, the result can be safely guaranteed. 



Very little actual photographic work has been 

 done in natural color under the magnification made 

 possible with the microscope. This is partly on ac- 

 count of the difficulties to overcome in getting sharp 

 enlarged images, in monochrome, over the entire 

 field with either direct or dark field lighting. These 

 difficulties are greatly increased with additional fac- 

 tors like natural color with its low range of correct 

 exposure, latitude, etc., making it difficult to get 

 perfect results, while the more versatile panchro- 

 matic film, allowing to some extent a correction in 

 the printing to correct errors in exposure, is usually 

 considered the Mecca of microscopic photographic 

 technique. 



As most of the microscopic subjects to be pictured 

 depend on slight variations in color to make them 

 visible to the eye surrounded as they are by other 

 matter the difficulties to overcome are very much 

 increased as the picture in monochrome does not 

 give a true rendering of the living subject. To the 



