5
Conclusions
The writer has attempted to show that compared with
what it could be, the amount of information obtained from
air photographs is very small indeed, and that this arises
from a lack of any rational approach to the problems of
exposure, processing, printing and viewing. The losses
are truly enormous. Large chunks of information may
first of all fail to register on the negative itself. Of
what is left, further large chunks fail to reproduce on
the prints, and of what is reproduced on the prints, the
resolution is degraded to two-thirds or a half of what it
was on the negative. Even this is not the end of the
deterioration because the reduced and degraded information
remaining on the prints is examined by usual practice, at
a magnification sufficient only to see the larger bits of
it.
One may well ask how it comes about that such a
state of affairs could be allowed to prevail, and why it
is that such seriously degraded photographs are accepted
without complaint. The explanation of this as far as
the negatives are concerned is that the user has no basis
for comparison. He does not know what ought to appear
on the negatives, and so has no grounds for complaint.
With regard to the prints, here again the user will
generally accept the prints he is given unless he has
reasons to suppose they are seriously inadequate, and
unfortunately he seldom compares them with the negatives.
If comparisons between negatives and prints were more
usual there would have been much less astonishment at the
additional detail produced in the open fields by controlled
dodging, because all this detail is to be found on the
negative.
These large information losses which occur in air
photography very much reduce the economy of aerial survey
procedures but it remains that the practical photogrammet-
rist is mostly unaware of them. Being unaware of them he
is untroubled by them, and so he gets ahead with his work
as best he can. The writer has attempted to indicate a
new and rational approach to what he has called the "Art
of Taking Air Photographs", leaving many details remaining
to be worked out. He believes however that further
advances in these procedural processes promis e to be more
rewarding than any other matters which are the concern of
Commission I.