457 - 
METHODS 
' , eine 
ind Obst- 
ldämmen, 
;ens ver- 
Dtographie 
Lchende 
2rt . 
The photographs were to be made on living brushwood. 
Since propagation of the disease is hard to control, infected 
plants must be eliminated at once. For this reason demonstra 
tion objects of fully diseased plants are scarce. 
The Schleswig-Holstein plant protection office pointed 
out two fire-blight areas near Husum, which were photographed 
simultaneously during one day (September 27, 1973). Ground truth 
nmen. Mit 
Brgestellt, 
ig der 
aben sich 
sen sich 
e Kombi- 
ifferenzen 
en lie- 
Kombina- 
en Dar- 
noch zu 
and aerial photographs were taken with two Hasselblad-cameras 
6x6 cm. Color-film (Agfachrome 50 S) and Color-Infrared-film 
(Kodak 2443) were both used. 
The aerial photographs were taken from the lowest height 
of 500 feet, delivering at a scale of 1 : 1500 a picture of 
80 x 80 m. At the time of exposure the weather was cloudy and 
rainy. 
We used the following methods of interpretation 
Color densitométrie measurements in single pixels 
ovora)• 
infections 
also ob 
stein . 
uit or- 
stein, 
plants. 
Density values D or transmittance values T, respectively, 
of the red, green and blue color portions of the interesting 
pixel on the film were determined with a color densitometer. 
Density and transmittance are linked by the equation 
D - log 
Fig. 1 presents transmittance values. Four groups of 9 different 
measurements are shown. They were made from close-ups of color- 
re-blight 
and color-IR-film. The transmittance scale goes approximately 
from 1 % to 65%. The healthy and sick leaves could be distingu 
ished on the images. Each diagram presents the values of the 
transmittance in the three spectral bands red (R), green (G) 
¡cts. The 
irrounding 
and blue (B). High transmittance values mean light points, low 
ones stand for dark points. 
.al prob- 
ioods and 
tiy research 
The upper section of fig. 1 shows a typical signature of 
healthy leaves on color-IR-film. The first step (R) represents 
in false color reproduction the infrared portion, which is 
relatively high. The second step (G) shows the red color portion, 
which has of course a low value. The third step (B) matches the 
green color portion of the leaves and has a high level in a 
healthy leave, partially even higher than the infrared portion.