ON THE QUALITY ASSESSMENT CRITERIA OF DENSITY INDICES 
FOR AERIAL NEGATIVE 
Li Ziwei 
Associate Professor 
Cao Hongjie 
Engineer 
Chinese Academy of Surveying and Mapping 
Beijing, 100039, P.R. China 
Commission I , Working Group 1 
KEY WORDS: 
Quality Criteria 
ABSTRACT 
Film, Aerial Negative, Density Indices, Microcharacter, Visual Character, 
This paper discusses the internal relation between tonal gradation character and visual character as 
well as the relation between the tonal gradation character and the microcharacter of aerial negatives. 
And also, a set of practical quality assessment criteria of density indices for aerial negatives has been 
proposed in combination with the statistic results of density range. 
1 Introduction 
As we know, the accuracy of photogrammetric 
mapping and the reliability of image 
interpretation depend on the quality of the aerial 
negatives or its copies used. The tonal gradation 
character of an aerial negative is usually 
described by image photographic quality which 
is assessed with density and contrast indices. 
Density and contrast indicate the control level of 
exposure and development, show the 
reproduction capability of luminance difference 
of the subject, control the image microcharacter, 
such as resolution, sharpness, Modulation 
Transfer Function (MTF) , and influence the 
accuracy of visual interpretation. So they are the 
main aspects of aerial photographic specification. 
Followed the principle that subjective 
assessment should accord with objective 
measurement, this paper discusses the internal 
relation. between tonal gradation character and 
visual character as well as the relation between 
the tonal gradation character and the 
microcharacter of aerial negative through the 
visual psychological series wedge experiment, 
the fuzzy judgement based visual assessment 
110 
experiment and the measurements of negatives 
density and microcharacter indices, such as 
resolution, acutance, RMS granularity, MTF, 
information capacity. And also, a set of practical 
quality assessment criteria of density indices has 
been proposed in combination with the statistic 
results of density range. 
2 Density and Its Visual Feature 
As far as a large number of aerial negatives used 
for plotting, the receiver of image information is 
visual system of human being, and what 
stimulates. visual perception is the variation, in 
brightness with the help of variant optical 
equipments. 
2.1 The sense perception of density 
The sense perception of density variation 
depends on the light flux passed through eyes, 
so does the brightness variation. The scientists 
have showed that: 
€ For human eyes, the amount of brightness 
perception is directly proportional to the 
logarithm of the brightness in proper range. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996 
  
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