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when 
ding 
, the 
sople 
mage 
hers. 
2 we 
7 for 
less 
and 
with 
am 1S 
t be 
10ng 
the 
  
resolution, enhance the reproductivity of details, 
and obtain high accurace, MTF and information 
capacity. Tab. 2 and visual assessment results 
show that the high contrast negatives possess 
abundant and fine density gradation. and have 
good visual effects although their Dax and Din 
are not good enough. The visual perception and 
steroscopic effects would be very poor when AD 
is less than 0.7. And the image tonality would be 
too hard to keep the details when AD is larger 
than 1.3. Thus AD should commonly range from 
0.7 to 1.3, and the optimal Contrast is about 1. 1. 
5.5 Fog density Deo 
In the  preconditions of the complete 
development, fog density Do should be as small 
as possible. When the fog density increases , the 
transparency of negatives would be poor, the 
detail contrast would be reduced, the image 
resolution would decrease, and the grainness 
noise would increase. So the fog density Do 
should not overpass 0.2. 
5.6 Processing gamma value 
Although the processing gamma value obtained 
from characteristic curve of wedge is used to 
appraise the control level of development, it 
need not to set limit to gamma value. Generally 
speaking, gamma value should not surpass the 
maximal value determined by the dynamic 
sensitometry, and it should be near the gamma 
value corresponding to the effective sensitivity . 
presented ahead of flying in order to match the 
development conditions with the exposure 
conditions. Additionally, processing gamma 
value plays an important role in adjusting 
contrast AD to the standard level according to 
the luminance difference of the subjective. 
From the above conclusions, we have proposed 
a set of assessment criteria of density indices for 
aerial negatives which are listed in Tab. 3. 
Tab. 3 The quality assessment criteria 
excellent 
Do <1) 
a ity D, 08~1.1 
minimal ity D >Dy+0.2 
maximal ity D <1.7 
contrast AD 09~1.2 
* contain the density of film support 
  
Reference 
[1] Walls H J. Attridge G G. Basic Photo 
Science, How Photography Works. Focal Press, 
1977 
[2] Cai Junliang. The Density Quality Criteria of 
Aerial Negatives. Serveying and Mapping 
Standardization, No. 1, 1989 
115 
ualified 
<0.2* 
06~1.3 
>D,+0.15 
<1.8 or 2.0 for ial 
07 1.3 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996