BOTANICAL PHOTOGRAPHY 177 



The relative positions of the various parts of the equipment as set 

 up for high-power work are given below: 



Ground glass 



Camera bellows 



Microscope 



Slide 



Substage condenser 



Light filter 



Auxiliary diaphragm 



Auxiliary condenser 



Water-cooling cell 



Auxiliary condenser 



Light 



MOVIE PHOTOMICROGRAPHS 

 By Dr. Paul J. Sedgwick 



Before the advent of the now popular 16 mm. amateur motion pic- 

 ture film, the cost of making motion pictures was prohibitive for most 

 workers. In screen time 100 feet of the amateur size film is equivalent 

 to 250 feet of the standard 35 mm. film. A further economy is brought 

 about by the fact that the 16 mm. film is a reversal film. There is no 

 extra cost for the making of a positive. The original film is developed 

 as a negative and then immediately converted into a positive by a 

 process of reversal. The entire charge for processing is included in the 

 original purchase price for the film. 



The 16 mm. film is being widely used in the preparation of teaching 

 material and is finding some use in the recording of the results of re- 

 search. Photomicrography with the motion picture camera is not very 

 different from ordinary photomicrography. For movie photomicro- 

 graphs at normal speed any good amateur motion picture camera will 

 serve. Most of the amateur cameras are equipped with spring motors 

 which operate the shutter so as to take 16 pictures or frames per sec- 

 ond. Many of the cameras have half-speed attachments and some have 

 slow motion attachments. With the half-speed attachment 8 frames 

 are exposed each second, and when the finished pictures are later pro- 

 jected, the speed of the action is then seen to be doubled. The slow 

 motion attachments found on some cameras expose either 64 or 128 

 frames per second which permits the slowing down of fast action. 

 Where time-lapse pictures are desired of such subjects as the germina- 



