hydrographical boundary 
delineation. The different 
infrared reflection 
characteristics of deciduous 
and coniferous forest canopies 
and the strong infrared 
absorption of water bodies 
provide the physical basis for 
the effects portrayed by the 
film [9, 10 ]. 
Panchromatic 
Panchromatic emulsions are 
generally attributed a spectral 
sensitivity similar to that of 
the visible light spectrum. The 
spectral sensitivity of these 
emulsions range between 400 nm. 
to approximately 670 nm. [11]. 
As true panchromatic emulsions 
only the Ilford aerial films 
qualify [12,13]. The Kodak 
aerial films are sensitized to 
approximately 720 nm. and are 
described as extended red 
panchromatic [7]. The Agfa 
aerial films are sensitized to 
about 760 nm. and are slightly 
infrared sensitive [14,15,16]. 
The ' panchromatic' category 
displays the widest choice of 
films, each varying in emulsion 
speed, granularity, resolution, 
and as noted, spectral 
sensitivity. From a user 
perspective, the subtle 
differences in spectral 
qualities and the inherent 
differences in graininess and 
resolution will have a 
significant impact on the image 
definition and consequent 
application. For ease of 
description the panchromatic 
category is subdivided into low 
speed, medium speed, fast 
speed, and very fast speed 
emulsions. The basis of these 
categories is obtained from the 
aerial film speed quoted by the 
manufacturer. Among these 
groupings the general tendency 
is for the granularity 
resolution characteristics of 
the films to improve as the 
emulsion speed decreases. 
Low speed emulsions. Three 
emulsions are currently 
available in this class. They 
are the Kodak Panatomic-X 
Aerographic II 2412 film, Kodak 
High Definition Aerial Film 
3414 and the Agfa-Gevaert 
Aviphot Pan 50 film. High 
resolution and low granularity 
are key attributes of the three 
films but the similarities tend 
to end here. 
The Kodak 2412 film is 
generally regarded as a 
relatively high contrast film 
with typical average gradients 
of about 1.6 to 2.0 [7,17]. 
Recent tests in Kodak Duraflo 
and Agfa G74c developers have 
not indicated otherwise (Table 
1). The high contrast of the 
film has generally prevented 
the widespread use of the 
emulsion, even in situations 
where higher contrast would be 
thought advantageous such as in 
small scale applications. In 
this case, moderate haze can 
nullify the film's higher 
contrast attribute. 
The Kodak High Definition 3414 
film is described as an 
extremely fine grain, slow 
speed, thin base film designed 
for high altitude 
reconnaissance [7]. Practical 
use of this very high resolving 
emulsion is limited due to its 
low sensitivity; the aerial 
film speed is in the order of 
about 8, or about 5 times less 
sensitive than the Panatomic-X 
film. 
The Agfa 50 film is generally 
lower in contrast than the 
Panatomic-X film with typical 
average gradients of about 1. 4 
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