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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
