INTRODUCTION 
Regular serial survey photography using large cam- 
eras and film and strict controls, is costly but necessary 
for the production of accurate base maps and interpretations 
over large areas. In the years between major aeri&l surveys» 
changes occur in the landscape features of local areas, be- 
cause of various processes of exploitation, construction or 
disaster. Some of these changes may be of vital concern to 
the forester, engineer, geographer, geologist and agricul- 
turist, but the cost of making frequent, local aerial sur- 
veys, using conventional techniques in order to maintain 
up-to-date information; can become prohibitive. Since the 
newly-developed landscape features of interest generally 
have continuous boundaries (e.g. forest cutover), these 
landscape features can be delineated by using photographs 
with less-than-optimum resolution. 
The quality of 35-mm cameras and films is now such 
that prints enlarged from 35-mm negatives can provide com- 
pletely acceptable details of landscape changes at a small 
fraction of the cost of conventional photography. This 
paper presents a technique of 35-mm supplementary aerial 
photography developed by the Ontario Department of Lands and 
Forests (Canada), with a discussion of desirable specifica- 
tions and other considerations. 
Furthermore, large-scale photography with motorized 
35-mm cameras receives attention. 
SUPPLEMENTARY AERIAL PHOTOGRAPHY (9.A.P. ) 
The prime purpose of S.A.P. is map revision, This 
may entail the insertion of new construction features, such 
as roads, power lines, industrial plants and other buildings, 
or the mapping of modified areas, such as forest burns or 
cutovers, landslides, glacial movement. 
The S.A. photographs are 6.2X enlargements (15 x 
22.5 em—6" x 9") of the standard 2h x 36 mm negative and are 
at the same scale as the conventional photographs. They are 
two-thirds the size of the conventional 22.5 cm (9") square 
print and of the area they cover (Figures 18, b). Normal 
overlap (60%) ensures that complete stereoscopic coverage 
is available and that the interpretation of these enlarge- 
ments proceeds normally. The interpretability of the S.AP., 
as with all other types of photography , depends on the res- 
olving power of the lens-film-processing combination. 
It should be understood that the enlargement of & 
negative cannot compete in image quality with the contact 
print of the same negative. The enlarging process involves 
another optical system and the magnification of the grain 
size in the emulsion. Still, with the right lens-film- 
processing combination, adequate resolution can be obtained. 
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