International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part Bl. Istanbul 2004 International
; ig Si = ; 4500 ——=
of photographic film; seven different exposure increasing by a am 12
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factor of 1.585 (log= 0.2) and represented by the seven bars in i 2m.
Figure 6 were simulated to investigate the information loss in * 3000 +
shadow areas comprised of densities between 0.2 and 0.6. ! 2500 4
É 2000 +
: a 1500 4
= 4 1000 4
2 t 5004
14 = 0 Mr
= 00 ü
" 4500 4777
P 4000 4
* ! 35004.
!
e 3000 4
! 2500 4.
t 2000 +
T » 1500
a 1000 4
t 500.
ne rte m — =
09 02 04 p6 0.8 1G 12 14 16 18 24 232 24 26 28-31 32 34 sé 5 00 f
1 log exposure
4500 {777
2 P 4000 —
fret ! 3500 -
3 e 30004
4 | 2500 4
ee] n
c 2000 4
L
enu Ly 9 1500 4
6 | » 1000 -
7 | t 500 +
E Ed m
pq
00 (
5 imaoe secti ; hvestionti ; et | 4500 4777
Figure 3. DMC image section used in the investigation Figure 6. Original subject range (#1), standard D-logH curve | P ned
for black-and-white negative film and seven | 45600 4
45 . t 3 | M TIS
P sm exposures (#1-7) used to derive densities for | ; 3000 -
nn] simulated images on film. 2600 of
xus | c 2000 4
e 3000 : ? 1500 {
| 2500 Figure 7 presents the histograms for the seven simulated pho- " 2
ES . . ~ vo . r li >
c 2000 tographic images; these were derived from densities obtained t 5004
d when the subject-range values shown on the abscissa are con- E m
1000 S = : 00 (
HA verted to 1mage densities shown on the ordinate. As a larger
= ~ . x ARnn IM
0 = part of image 1 includes the base-plus-fog (B+F) range, a com- ; fsbo s
T T T T T . pr . - 4000 4
500 1000 1500 2000 2500 3000 3500 4000 pressed histogram results. The increase in exposure first re- en
Grapevel Values duces the part of the subject range falling into the B+F range 239004.
. : as . . * 3 e cl Le essaie 2 : E ; | ce,
Figure 4. Histogram of the initial intensity image and spreads the histogram (images 2 to 4) and then simply 2500 -
moves the histogram (images 5 to 7). It should further be noted, | c 404
. ~ . 2 1500 +
4500 4 that the density range for the latter images does not exceed ~ | " 4000 |
. ~ . . r b
P 4000 - 1,0 as required for aerial negatives. | t 50
E |
, 35004 | o 2
: 3000 4 Inspection of the same magnified shadow area in the seven im- | a t
zm 7 ages for subject-range densities between 0.2 and 0.6 located for | 4500 {7
c 2000 - s . ; > 4000 À
© sm exposure | and 2 below the of the "first useful point" located | On
| ! 3500
^ 1000 4 where tana. — 0.2 suggests for exposure 1 a total replacement of | * 2000 À
t 500 4 image content through noise whereas in image 2 the image | | 2500 4
N 002.040 05001218, 96.06.05 10.12.14 16.19 20.22 01 76 280 content can already be recognized; it becomes clearer in images | C 20004
00 02 04 06 08 10 12 14 16 18 20 22 24 26 238 30 ie TL roa: : ; : © 15004
Tonal aval Folios 3 to 7. This result indicates that the first useful point on the A
Figure 5. Histogram of the derived negative density image characteristic curve could be located where tana « 0.15. ME
p E
The effect of the conversion from reflectance values assuming a With a density range of — 1.0 there is danger of loss of infor- 00 (
subject range of 1000:1 as used for high-contrast resolution mation in the highlight areas of the image. 4500 777
targets and transmission density step tablets is seen on the his- pu
s ii. ; 5 ; 5 3500 —
tograms for the original intensity image (Figure 4) and the * un E.
resulting density image (Figure 5). The bar labelled 1 in Figure | anno dee
6 shows the subject range for the used image section in c 2000 4
densities. | © 15004
| " 1000.
| n
. . . t 00 4
The values in Figure 4 range from 4095 to 91; this corresponds | 4
- . ye Yr
to reflectances from 1.0 to 0.0222. The derived densities range 20 |
from 0.0 to 1.653. Using the DlogH curve used to define the
sensitometric characteristics of black-and-white negative film Figure 7. 1
f
(Figure 6) these densities were transformed to include the effect
