CHAPTER XIV 



BOTANICAL PHOTOGRAPHY 



The only field of photography with which histology is directly con- 

 cerned is photomicrography, together with paper prints and lantern 

 slides made from photomicrographic negatives; but this field is so 

 difficult that time, temper, and money will be saved by beginning 

 with pictures of trees, flowers, buildings, maps, graphs, lantern slides, 

 and such experimental apparatus as one needs in illustrating investi- 

 gations. 



It is assumed that the student knows something about an ordinary 

 camera and that he knows the usual routine of making negatives and 

 paper prints. 



The first step is to get a good negative. Begin with a tree or a build- 

 ing. The most important factor in securing a good negative is correct 

 exposure. The professional photographer does not need any meter, 

 but the rest of us had better use one to determine the length of expo- 

 sure. 



The Watkins Bee Exposure Meter is good and inexpensive. The 

 sensitive paper is reliable for a year, even in the tropics. The Wynne 

 Infallible Exposure Meter lives up to its name. The Harvey and the 

 Voigtlander are good meters of the mechanical type. The Bewi and 

 the Justaphot are more expensive, but they almost remove the neces- 

 sity for judgment in making exposures. The American Photography 

 Exposure Tables are very convenient and instructive, since the various 

 factors, light, stop, plate, latitude, and time of day, are estimated 

 separately. The tables give also practically all the formulas and direc- 

 tions an amateur needs. An amber-colored filter, increasing the expo- 

 sure about three times, will keep the clouds, which would otherwise be 

 lost, and will give much better color values. 



Next, select a good plate or film. Professor Land, when asked his 

 opinion of the comparative merits of film packs and cut films, said, 

 "Packs cost twice as much as cut films and are only half as good: 

 plates are better than either." But films are improving and the cut 

 film now has an emulsion as good as that on a plate. Such an emulsion 

 cannot be put on a roll film or film pack, because the film has to be 



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