(37) 
selecting camera temperature from 45°F to 75°F and controlling it within ± 10°F. 
The Coast and Geodetic Survey report uncontrolled ambient conditions ranging 
from —10 to 0°C and from 10% to 40% relative humidity. 
VI. NEGATIVE MATERIALS AND PROCESSING 
Introduction 
High speed panchromatic materials are still the most generally used although 
for some purposes slightly slower, finer-grained materials are preferred. 11 would 
be informative to have this preference verified by resolution data, with due allow 
ance for the necessary increase in lens aperture. 
Film is used for most of the work, but plates have dimensional stability 
advantages which justify their inconvenience for some uses. Any major improve 
ment in film bases would alter this. 
Continuous processing machines are in increasing use. However, the 
relatively non-uniform development obtained with rewinding machines is 
tolerated for some uses to obtain small size and portability. Sensitometric 
control of processing is not in as general use as would be expected. 
Australia 
The film used is Kodak Super XX on topographic base. It is processed in 
a hand-operated, reel tank with solution temperatures between 65°F and 75°F. 
No routine sensitometric control is used. Storage conditions before exposure 
are 50°F, 60% relative humidity. 
Austria 
For topographic photography with the Wild RC-5, Kodak Super XX film 
is used. It is processed with an automatic rewinding developing unit and an 
automatic drying apparatus to a gamma of 1-2. Solution temperature is 18°C. 
For cadastral survey with the Wild RC-7, Avio Microgran plates are used. They 
are processed in a tank developing unit at 18°C to a gamma of 0-8. No routine 
sensitometric control is used in either process. 
Canada 
For all aerial photography Kodak Super XX topographic base film is used. 
When this film is processed to a typical gamma of 1-2 in Kodak D19 or D19B 
developer, a resolving power of 25 lines per mm is obtained for a 5 line target 
with density difference 0-2, and a light source equivalent to mean noon sunlight 
modified by a Wratten # 12 (minus blue) filter. I he ASA exposure index 
for this film is 100. It has been suggested by Howlett 22 - 23 that the philosophy 
behind the ASA speed is not applicable to most aerial photography. A criterion 
based on a curve between log exposure and resolving power is suggested with the 
speed number based on the minimum exposure required to give 90% of maximum 
resolving power using a target with density difference 0-2 and the above illumin- 
ant. For one sample of aerographic Super XX this minimum exposure was 
determined to be 0-0062 metre candle seconds. As a convenient speed value