different camera positions (fig.1). The test-object consists 
  
Of a dyke planted with four rows of poplars of the same age 
but occuring in different topographical positions. It was 
important to select a dyke for which the orientation allowed 
to evaluate the influence of radial displacement, differences 
in illumination and the influence of background radiation. 
The densities of each emulsion layer have been measured using 
a Kodak Color Densitometer 10 K. They have been expressed as 
percentages and these have been represented in delta diagrams 
(fig.1). These percentages refer only to the relative diffe- 
rences between the colour dyes in each layer of the emulsion 
and not to the percentage of spectral reflectance. 
Decreasing values of "red density" means a decrease of cyanic 
dye in the infrared-sensitive layer, resulting in a more 
reddish colour here on the photographs related to a higher 
reflection of infrared radiation. 
In stereoscopy the same object is seen from two different 
positions resulting in different radial displacements. In the 
example shown camera position 2 corresponds with a location 
in the centre of the photograph and the densities of the 
trees are represented by black symbols (nr.1,3,5,7,9,11,14 
and 16). Camera position 1 looks upon radial displacement 
images and also in relation with the direction of the suns 
rays, upon the shadowed part of the canopies. 
Furthermore the background of the photographical image for the 
trees becomes different. In camera position 2 allrows-are 
seen with grass as background. In camera position 1, row A 
gets a ploughed field as background radiation (having a 
blueish hue). 
The images of the other rows are displaced upon each other 
so that, for example, row B gets the canopies of row A as 
background. 
The deltadiagrams show that generally spoken camera position 
2 gives a more saturated reddish or purplish hue than in 
position4 , and this is referred to as objects positioned 
in a high contrast (Case of trees nr.2,4,6,98,10,12,. ).The 
influence of the background radiation becomes also evident.