ADVANCES IN SENSITIVE MATERIALS AND TECHNIQUE FOR AIR PHOTOGRAPHY
Dy
G. C. Brock, M.Sc. , F.R.P.S."
SUMMARY
A brief review of progress in some negative and positive materials
and some lenses used for air photography.
Modern negative materials ere faster with much better keeping quali-
ties, and some useful slow fine-grain emulsions are becoming available.
Sensitometric data and results of some tropical keeping tests are given.
Bromide papers show improvements in usable density range and curve
shape, but further improvement would be welcome, especially in the soft
grades. Improvements have been made in the resolving-power of some water-
proof papers.
Resolving-power figures for a modern type of survey lens on fast and
slow film are given, and it is concluded that previous advice to use the
fastest film at a small lens aperture no longer holds good universally.
INTRODUCTION
Some years ago the writer published a book which discussed the fac-
tors making for good image quality in air photography. The spur for this
enterprise was provided by his conviction that the essentials for good
photographic technique were taken too lightly, as evidenced by the poor
quality of so many of the air photographs that ceme his way. Al though
the book could not be published until 1952 it was essentially based on
work done up to 1946 and this paper takes note of the progress achieved
over some ten years by the manufacturers of sensitive meterials and lenses,
progress which allows a generally higher standard of air photography to be
achieved under favourable conditions. It is perhaps worth pointing out
that proper illumination and a clear atmosphere remain the most important
of all factors essential for good air photography and that no amount of
technical progress will change this situation. Technical advances do
enable us to obtain acceptable results under more difficult conditions and
even better results under good conditions, but not good results under bad
conditions.
* Royal Aircraft Establishment, Ministry of Supply.
