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The second section of fig. 1 shows measurements of healthy 
leaves on color-film. In this case, the second step (G), which 
matches the green color portion, has the highest level. The red 
and blue portions are expectedly lower than the green one. In 
some cases the red level is a little higher than the blue one. 
The third and fourth section of fig. 1 refer to the mea 
surements of sick leaves. 
Section three for the color-infrared-film represents a 
relatively high IR-level. The green level, representing the red 
portion of the leaves, is lower. But the blue level, that is 
the green portion of leaves, gives the lowest value. 
The fourth section of fig. 1 shows sick leaves on color- 
film. The gradation allows clear recognition ot the ginger color 
of the sick leaves. 
Altogether fig. 1 shows clearly on both types of films the 
different reflectance of healthy and sick leaves. The single 
step combinations within one section are very similar and allow 
the classification. 
The progress of the disease, however, could not be detected 
by measurements of the transmittance. 
Cluster description 
With the above described measurements the 6 graphics of 
fig. 2 were gained. For this two color densities of the same 
pixel were plotted, the density scale going from 0.2 to 2 
approximately. 
In fig. 2 we see the so called clusters. Healthy leaves 
are marked by points, sick leaves by crosses. If the two clusters 
of a graphic superpose, the separation of healthy and sick ob 
jects is not possible. In fig. 2 this is the case at the combi 
nation green-blue and blue-red of the Colorfilm. On the other 
hand the clusters of the combination green-red for the Colorfilm 
are designated on both sides of the diagonal so called color neutral line. 
This means for the combination green-red, healthy and sick leaves can be 
distinguished, with the healthy leaves giving a positive and the sick leaves 
giving a negative value.