The mo3t important quality of the subject photographed
which determines exposures and development is its maximum
and minimum brightness. We have a3 yet no instrument to
measure these. In consequence usual procedures are based
extensively on guess.
Comm. 1. The Art of Taking and Examining Air Photographs
J. A. EDEN
Abstract
The art of taking and examining air photographs has not
kept pace with advances in cameras and emulsions and is
responsible for very large and unnecessary losses of informa
tion. The defects of present practice are examined.
Various suggestions are made for improvement, and a plea is
made for more intensive research into this important aspect.
1. General Commission 1 has frequently discussed cameras and
films, their various properties, and how to determine their
characteristics, physical features, and image producing
capabilities. As a result of these considerations, both in
the Commission and outside, there have been enormous advances
in instruments and materials. Our cameras now have wider
fields of view, better shutters, larger apertures, better
light transmission, less distortion and higher resolution
than ever before. Films available now have greater speed,
finer grain, better tonal rendering, increased stability and
greater versatility. We may now. take photographs in black
and white or in colour and it may be said that advances in
these fields have been enormous and very worth while.
1.1. It remains however that to obtain photographs and to
inspect them in such a way that the finest details can be
seen, one has to carry out certain procedures. The film
must be exposed and processed, and prints must be made and
examined. This I call "The Art of Taking and Examining Air
Photographs' 1 , and this art, with some minor exceptions, has
remained largely unchanged since air photography seriously
commenced in the early 1920s. This state of affairs is not
satisfactory. It is responsible for the fact that although
it is now possible to obtain laboratory resolutions,
enormously exceeding those possible in the early days of air
photography, in practical work, the end product does not
approach the improvement that might be expected from the
enormous advances in instruments and materials.
The rest of thi3 paper will deal with the art of taking
photographs under three headings - The Negatives, The Prints,
and The Examination. The defects of currently used
procedures will be discussed, and various suggestions will
be made for improvements.
The Negatives
2.1• Usual Methods of Exposing and Processing