(D 
Q) 
mined 
| with 
(3) 
(4) 
(6) 
  
  
Yuri Knizhnikov 
2.2 Experimental estimation of the discrete space images representation properties 
Experimental estimation of the proposed equation (formula 6) consisted of: 
- A/D conversion of the photographic test objects which photographic densities were measured; 
- determination of the relationship between produced digital test objects luminance and initial image test ones 
photographic (blackening) density; 
- microphotometry of the linear photographic test objects, characterized by a different resolving power, and calculation 
of theirs initial photographic contrasts; 
-A/D conversion of the photographic linear test objects under given scanning aperture and sampling rate sizes (b and d) 
and photographic densities analogs determination of the produced digital linear test ones. 
A relationship between discrete test objects luminance / (in gray levels from 0 to 255) and their photographic density pr 
has been established as result of the first and the second experiment stages. Plot of this relationship is shown in figure 2. 
Ir 
L00 4 
090 — 
0,80 — 
  
070 — 
0,60 — 
0,50. À 
0,40 — 
  
  
030 — 
020 4 M. 
010 — C 
bh bh 
T T T T I I I I | | 
20 4 60 80 100 120 140 160 180 200 220 240 / 
  
  
  
  
Figure 2. Plot of the relationship between discrete test objects luminance / and their photographic density D 
Then initial photographic contrasts AD" have been calculated under the different resolving power (R) in agreement with 
formula 4 (table 1). These calculations were made due to scanning plots of the linear photographic test objects. 
  
Resolving power Photographic contrasts of the linear test objects Values of the modulation transfer 
  
  
  
  
  
  
  
  
  
  
of the linear test function 
objects R, mm” Initial image Discrete image Theoretical Empirical 
np" Theoretical Empirical T(R) TA (R) 
values DD“ values D, 
25 0,82 0,73 0,69 0,89 0,84 
30 0,73 0,61 0,58 0,84 0,79 
35 0,57 0,45 0,42 0,79 0,74 
40 0,43 0,32 0,28 0,74 0,65 
45 0,34 0,23 0,21 0,68 0,62 
50 0,25 0,15 0,14 0,61 0,56 
  
  
  
  
  
  
Table 1. Representation properties of the initial and discrete (digital) linear photographic test objects 
An analogous characteristics of the produced digital linear test objects AD“ have been obtained under 0,0075 mm 
scanning aperture and 0,0075 mm sampling rate. Theoretical contrasts AD“; have been calculated as: 
AD“; = AD"; - T(R;), (7) 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 503