6 
It is common practice with geologists to resort to spectrozonal films whenever the 
territory to be photographed happens to be covered with vegetation typical of the soil or 
underlying rock. 
The CH-2 film may also be recommended in many cases of soil studies, differences in 
moisture content, humus components etc., being easily distinguishable on it; but colour 
films are by no means infrequently used either. 
Aerial colour photography using various films is also executed in town surveys, surveys 
of agricultural areas, for planning railway lines, designing hydrological projects and for a 
variety of other purposes. 
In conclusion the problem of some rivalry between the black-and-white and the colour 
films should be mentioned. 
The former is still the more commonly used in aerial photography in spite of the ever 
growing part played by the colour-films, because the latter are only employed where their 
advantages over the black-white films are self-evident. In a number of cases it is a good 
plan to make black-and-white prints from colour films for this results in a better rendering 
of details than is attained with black-and-white negatives. 
It should also be added that colour films have become widely used in aerial surveys in 
the U.S.S.R.; the scope of colour air surveys is steadily growing, there being a notable rise 
both in the quantity and the quality of work done. 
REFERENCES. 
[1] Yordansky, A. N., I. The Uses and Principles of Spectrozonal Photography. 
Zhurnal nauchnoi i prikladnoi fotografii i kinematrografii (The Journal of 
Scientific and Applied Photography and Cinematography), Vol. II, Nr. 1, 1957. 
II. Chromatic and Achromatic Details of Darkening!) as a Measure of Spectro- 
zonal Images Mutually Aiding to Make Themselves Appreciable. Ibid, Vol. III, 
Nr. 4, 1958. 
[2] Mikhailov, V. Y., On the Rational Way of Using the LN 3 Negative Colour Film. 
Ibid, Vol. III, Nr. 5, 1958. 
[3] Mikhailov, V. Y. and Tziganov, M. N., The Colorographic Process in Air Photog- 
raphy. Trudy ZNIIGAiK, Publication 107, 1955. 
[4] Uspensky, A. N., Photo-electric Printers for Colour Photos. Geodesya i Karto- 
grafya (Geodesy and Cartography), Nr. 9, 1957. 
[5] Mikhailov, V. Y., Results of Employing the Colorographic Process in Air Surveys 
and Mapping. Trudy ZNIIGAiK (The Proceedings of ZNIIGAiK), Publication 
107, 1955. 
[6] Goldman, L. M., The Application of Colour Airphotos in Studying a Terrain. Ibid, 
Publication 137, 1960. 
  
1) i.e. the difference in optical densities between two adjacent elements of a photo image. 
  
  
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