to 1. 5, although the range 
varies greatly depending on the 
processing conditions (Table 
1). This film is gradually 
replacing its predecessors in 
small scale aerial 
applications. Its lower 
contrast, its ability to 
penetrate haze due to its 
slight IR sensitivity, high 
resolution, and low graininess 
are all factors working in 
unison to provide an excellent 
small scale product. 
Some work has been done in 
using both the Kodak 2412 film 
and the Agfa 50 film at medium 
scales in forest inventory 
applications. The performance 
of the Agfa 50 film was average 
in this regard, but definite 
potential was seen with the 
Panatomic-X film; it rated 
second in preference only to 
the Kodak 2424 IR film [8]. 
Medium speed emulsions. 
Three films are currently 
available in this class. They 
are Ilford's FP3, Kodak's Plus- 
X Aerographic 2402, and Agfa's 
Aviphot Pan 150. These films 
are typically used in small 
scale applications due to their 
relatively slow film speed, 
however, with the advent of 
forward motion compensation 
cameras, medium scale 
applications are now also 
becoming viable. 
The subtle differences in the 
films' spectral sensitivity is 
one important factor which 
establishes their most 
appropriate application. For 
example, in small scale 
applications where haze may be 
a hindrance in the proper tonal 
rendition of the terrain, the 
Agfa 150 film's sensitivity to 
760 nm. significantly improves 
the quality of the imagery 
(Figure 2). Visual comparisons 
of graininess and image 
sharpness also tend to favor 
the Agfa emulsion (Figure 3), 
however, due to recent 
findings* the matter remains 
open. 
The Ilford FP3 film, whose 
spectral sensitivity falls 
below both the Kodak and Agfa 
emulsions, would probably be 
inferior in cases where 
atmospheric haze required 
adequate penetration, but this 
film does have its merits. The 
average gradient of both the 
Plus-X film and the Agfa 150 
film tend to be quite high 
[7,17] (Table 2), but the FP3 
film displays an opposite 
tendency (Table 2). The normal 
average gradient of this film 
seems to be about the 1.0 
value. In addition, resolution 
tests performed by Wild 
(Heerbrugg) place this emulsion 
above either the Plus-X or the 
Agfa 150 film**. The FP3 would 
be advantageous in regions of 
high brightness range 
conditions such as mountain 
forests with alpine meadows and 
exposed bedrock or in glacial 
studies, but its utility would 
have to be judged according to 
the severity of haze 
conditions. 
Fast speed emulsions. This 
category comprises of three 
films: Ilford's HP5, Kodak's 
Double-X 2405, and Agfa's 
Aviphot Pan 200. 
■* 
J.Cummings, Kodak, personal 
communication, Nov. 1989. 
F.Zuberbueh I er, WiId, 
personal communication, May 1989. 
762