Figures 6 and 7 show for both lens cones the AWAM for f:4
and f:5.6, for 20 Lp/mm (larger terrain features), 40 Lp/mm
(medium features) and 80 Lp/mm (smallest features).
Note, that there is only a minimal performance improvement
from f:4 to f:5.6, therefore the full quality potential is available
already for the largest aperture.
30/4NAT-S Lens cone: AWAM |
Lens N? 17118
|
0.70 | |
|
|
AWAM (contrast)
0.10
£:5.6
m20 Lp/mm [M40 Lp/mm [80 Lp/mm
Figure 7
Spectral transmission and intensity homogeneity
Light distribution in the film plane should be as homogeneous as
possible over the whole spectral range covered by the usual
emulsions used in practice. This is important for medium or
small-scale photography with high-contrast colour reversal
emulsions (diapositives) over flat contrastless terrain. Also for
large-scale photography this physical optical characteristic plays a
major role in the image registration, as directly related to the
contrast and sharpness rendition.
Figure 8 shows the polychromatic transmission of both lens types
(for max. aperture f:4) as a function of the radial distance across
the film plane. The transmission values are deduced from
measurements taken between 380 nm and 900 nm.
Spectral light distribution in image plane
forspectral range 380 nm - 900 nm and aperture f:4
100
90 |
80
70 .
60
& 50 | i
5 |
40 . |
30 |
20 |
10 ..: |
0 i |
0 40 60 80 100 120 140
Radial distance (mm)
Coma | S/QUAG-S — A— 30/4 NAT-S
Figure 8
A partial compensation of the light fall-off in aerial lens cones is
realised by an "antivignetting (AV) layer", which is a neutral light
absorbing layer whose transmission increases from the optical
axis to the image corners. In the 15/4 UAG-S such a layer with a
standard AV factor 2x is applied on all filters, whereas in the
180
30/4 NAT-S an AV 1.4x layer is applied as a coating on the inside
surface of the upper front lens.
The remaining intensity drop is further attenuated by the
"skylight", as a non-image-forming diffusing atmospheric effect
which increa-ses with the incidence angle. Note that for critical
conditions (essentially for colour reversal emulsions) depending
on terrain type, illumination contrast and haze, higher factor AV
3x filters are available on request for the 6" lens.
The intensity drop should not vary for different spectral
bandwidths, otherwise shifts in colour rendition result between
image centre and image corners.
Resolution of the new lenses
When designing the new lenses 15/4 UAG-S and 30/4 NAT-S
Dr Klaus Hildebrand placed special emphasis on low contrast
rendition. This quality is essential for small-scale photography
with hazy atmosphere and for large or medium scales, where
details in shadows can be perceived with more accuracy and
reliability in the restitution phase, thus reducing mapping time
and costs.
Figure 9 shows the mean AWAR values for Panatomic-X 2412
emulsion determined with:
- high contrast test targets (3-bars test targets according to ANSI
PH3.609-1980 R1987), contrast 100:1 (log k=2), at f:4 and f:5.6.
- low contrast targets, contrast 1.6:1 (log k= 0.2) at f:4.
AWAR Resolution of 15/4 UAG-S and 30/4 NAT-S
| 140
120 —
100 +- D. x
80 4
60 —
AWAR (Lp/mm
40 1 3 200
20 . Brel
15/4 UAG-S
30/4 NAT-S
m f:4, high contrast [f:5.6, high contrast gg f:4, low contrast
EC TIER U
Terrain features with total contrast (object * illumination) 100:1
are rare in current survey flights, whereas contrastless objects with
short shadows at high sun angles (e.g. desert regions) or high-
altitude flights with hazy atmosphere require the highest possible
low-contrast AWAR, which why for both lenses the highest
AWAR is already made available at full aperture f:4.
TEST FLIGHTS WITH 15/4UAG-S AND 30/4NAT-S LENS
Three test flights realised on 06.09.94, 01.09.95 and 25.10.95
with the very large image scale 1:2500 made it possible to assess
the image quality and geometric accuracy of a serial production
15/4UAG-S and 30/4NAT-S lens cone. In the flights with the
15/4UAG-S, the PAV30 Gyro-stabilized mount assured
verticality and rotational stabilization of the RC30 camera.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996
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