463 - 
DIFFERENCES OF COLOR DENSITIES 
With the above described equipment finally differences 
of color density were measured and documented with the paper 
recorder. Fig. 4 shows the results. Here the sick parts show up 
distinctly. This is proven by comparison of figure 2. In both 
figures there is on the left side color-IR-film, on the right 
side color-film. Color differences go from top to bottom G - B, 
G - R and B - R. 
The cluster of the sick plants below the diagonal line 
in fig. 2 corresponds to a positive impulse of the recorder in 
fig. 4 and vice versa. Results to be expected from fig. 2 are 
proven in fig. 4. We achieved the same results at another four 
examples. However, it has to be noted that a road gives similar 
effects as fire-blight if only the difference of two color den 
sities are considered. 
Our method for classification of certain objects by deter 
mination of color density differences therefore has to be ex 
panded to several difference measurements in narrow spectral 
bands. 
CONCLUSIONS 
Measurements have proven that the classification of sick 
and healthy leaves of hawthorn is possible. This is achieved 
by regularities in the density differences between different 
spectral bands. These differences are gained by color densito 
métrie measurements on photographs. 
For these measurements color-IR-film is more suited than 
color-film. Especially evident are intensity differences be 
tween the red and blue part of the spectrum (actually infrared 
and"green). 
Similar regularities, however, exist on images of other 
healthy kinds of vegetation. Because of the multitude of vege 
tation therefore misinterpretation of aerial photographs is 
possible. 
Additionally, resolution of photographic and radiometric 
sensors is not high enough to encounter and separate the signa 
tures and structures of single leaves by aerial reconnaissance.