a — — 
In the positive processes the “Photosvet” (“Photocolour”) paper of the usual kind is 
used. It is available in two grades, viz. the normal (y is in the neighbourhood of 1.5) and 
the one with an enhanced contrast (y is about 2.0). The positive film of the same kind is not 
used as frequently. Spectrozonal colour film (SB) and the positive two-layer film (SP) are 
also available; they are used in printing from spectrozonal negatives. The lower layer is 
panchromatic and is rendered light blue upon development; the upper is orthochromatic and 
becomes magenta-coloured; the intermediate yellow filter layer is absent. In spite of special 
positive papers for printing from spectrozonal negatives being available, it is common 
practice to print them on three-layer papers, for the yellow layer enhances the variety of 
tones. 
2. For colour photography the same cameras are used as for black-white; it is advisable 
to employ conventional lenses. When using wide-angle (20 — 100^ or 120^) cameras, 
neutral “shaders” 1) should be introduced the density distribution of which is the reciprocal 
of the light distribution in the field of view. Light filters are indicated only for the SN-2 
film, which makes it suitable for taking photos from high altitudes. The CN-film is used 
without any filters or with a very faint-yellow one (JS-3), so it is not recommended for 
flying altitudes exceeding 3,000-3,500 meters. A filter of greater density (JS-12) has been 
experimented upon in conjunction with a film whose spectral characteristic conforms with 
tungsten lamps (LN-3) [2]; the results are satisfactory, but have not yet found their way 
into practice. 
To prevent changes in daylight spectrum from affecting the colour balance it is 
advisable to take colour photographs when the altitude of the sun is at least 20°. 
To avoid flare (diffused light) coated lenses and lens hoods may be helpful. 
3. The well known technique for processing colour films, commonly made use of in the 
treatment of movie films, is hardly practicable in the field. That is why the processing of 
aerial colour films follows the method developed at the ZNIIGAiK 2) [3]. This differs from 
the one employed in cinematography in what follows. 
a. The development of the film is carried out to the end; the “additional” development 
while rinsing after the development proper is thus dispensed with. The film is developed 
at once up to the required gamma (y) value which is controlled by the amount of the 
developing agent introduced and the length of development. Temperature changes may 
be considerable but they are allowed for, just as they are in the case of black-and-white 
films. 
b. The formula for the developer has been modified to a certain extent. The same agent 
(ethyloxyethylparaphenylenediamine) serves in both the negative and the positive 
processes; it is introduced into the stored solution just before starting the development. 
Sodium carbonate is substituted for potassium carbonate because it is more handy in 
the field. Potassium bromide is all but dispensed with; a much more effective buffer 
is used instead, viz. benzotryanol, the quantity of which may be 3 to 15 milligrams per 
litre. The optimum quantity for any particular case is found by trial before doing the 
actual work. As this buffer prevents fogging, one can, by prolonging the time of 
development, get a higher emulsion speed than that obtainable when using potassium 
bromide. (Fig. 3.) 
€. A strong hardening bath is used, so colour films can be processed in any regions, even 
when the temperature is high. A film will stand development without hardening up to 
30? Centigrade. Upon development it is transferred to a solution containing 0.5 per cent 
of acetic acid and 5 per cent of hypo (sodium sulphate) ; after this it is immersed in a 1 
  
1) Filters casting shadows on to the image plane. 
2) The Central Research Institute of Geodesy, Aerial Surveying and Cartography.