- 587 - 
The slicing of a single band photography can be very 
interesting but not sufficient for many purposes like those 
of the pattern recognition technique. 
By comparison of slicing corresponding to different bands, 
the "cross density slicing" is obtained ( Fig. 1 ). 
In this case, we are solving the system given by three e- 
quations: 
.nfrared 
i to that 
band A = constant 1; band B = constant 2; band C = constant 3 
.e the se- 
The capability of recognizing different targets increa 
ses strongly. If we divide each band in M density levels and 
Lon (that 
is to 
:al images 
n bands are considered, the number of the possible systems 
or combinations is given by: 
N = M n 
As an example with 3 bands and 10 isolevels we can di 
stinguish 10*= 1000 different targets by their color tona 
lities . 
bands is 
c)"Masking" and "masking slicing" of two bands. 
} in black 
», green, 
Considering band A in b & w positive performance and 
band B in negative, by overlapping A on B the resulting 
ying a par- 
y projec- 
density of this compound is: 
Density A + density (-B) 
but density (—B) = constant - density B 
but density = log exposure = log ( reflectance x time ) 
sors of 
e respec- 
ge, where, 
bution of 
and with time constant over the whole photography 
density = log exposure = log reflectance 
density A = log reflectance of band A 
density B * log reflectance of band B 
ne depen- 
ular kind 
mages re- 
ght) of 
an image 
irpretation, 
but negative of B is egual to: 
constant - B = K - B 
density (—B) = density(K - B) 
A 
log = density A + density (-B) . 
Subdividing the log-^- is isolevels we obtain the series: 
B 
>and can 
, in iso- 
: is achie- 
; level 
j time whi- 
3 ity of 
log — = K. ....... .K 
^ B 1 n 
that is : 
A K <4 K a _ u 
— e e H 1 H n