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The purpose of the present study was to ascertain the effects of
heat on commonly used aerial films and to establish some guidelines for
their use in warm environments.
3.1 EXPERIMENT
Six types of Kodak aerial films were included in the study: 2402
(Plus-X Aerographic), 2405 (Double-X Aerographic), 2424 (Infrared Aero-
graphic), 2443 (Aerochrome Infrared), 2445 (Aerocolor Negative), and
2448 (Ektachrome MS Aerographic). For each emulsion, samples were
heated in one of three ovens set at 50, 60 and 70°C respectively -(+2°C)
for durations ranging from 2 to 192 hours in an approximately geometric
progression. These heat exposures were selected on the basis of a
preliminary trial experiment as combinations causing significant film
effects, as well as being in a range that might occur under practical (4
conditions. Sealed containers were used during heating and cooling
periods to maintain constant humidity.
Step wedges were imprinted on each film sample by a calibrated NRC
sensitometer both before and after heat treatment. The light source
was Standard Air Photo Daylight®. The infrared films Were exposed
through additional filters to simulate normal use: a Wratten 12 for
2448 film, and a Wratten 89B for type 2424. To avoid latent-image
fading complications, light exposures were made on all film samples at
once before heating, and also after heating, following a six hour
minimum cooling period, and developed no less than thirty hours later.
Processing by continuous-processing machines (following standard
operating conditions) was carried out by the Reproduction Center of the
National Air Photo Library. :
Step densities were measured with a Macbeth TR-524AM densitometer.
Calibrated status A densitometry was used for the colour reversal
films, and calibrated status M densitometry for the colour negative
film. (a
The resulting data were used to plot H. and D. curves, from which
sensitometric properties were determined. For the monochrome materials,
C.S.A. standard Z7.3.2.1-1969 was used to compute film speed and
average gradient. The colour negative film (2445) also was analyzed
according to this method, treating each colour layer as a B/W emulsion.
The speed and gradient of colour reversal films were determined in
accordance with ANSI standard PH2.21-1972.
"Fog level" was taken as the density of unexposed portions of film
. Samples, and hence is opposite for reversal and negative materials.
A fourth criterion, consistency of colour balance, was used for
the color films. The definition of colour balance used by the Canada
Centre for Remote Sensing (CCRS)? was adopted:
