The Basic Principles of Photography

The ideal season of the year varies according to the subject being photographed. In April, in the northern hemisphere, it is fairly easy to distinguish fertile soils since plant life takes hold rapidly while, if we wish to discriminate between types of vegetation, autumn is preferable. After a rainfall, when the air has been washed clear of suspended dust, higher contrast plates can be taken. A slight breeze helps to show up water pollution, probably because of differences in density. 

These considerations must be borne in mind when we are working on satellite records, especially television plates, and data from the near infrared, up to around 2.5 m. 

In general terms, a colored filter attenuates the influence of the color complementary to it, and favors the spectral band corresponding to its own color. 

In satellites, the filters are placed on the TV camera lenses. Filter No. 12 is the most frequently used. The TV photographs from Nimbus 3, due to the yellow filter known as minus blue filter , are characterized by the striking contrast of the cloud forma- 

Filter type Wavelength attenuated + or — Favored Exposure indexes  

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