Chapter I: Preface

Airplane photography had its birth, and passed through a period of feverish development, in the Great War. Probably to many minds it figures as a purely military activity. Such need not be the case, for the application of aerial photography to mapping and other peace-time problems promises soon to quite overshadow its military origin. It has therefore been the writer's endeavor to treat the subject as far as possible as a problem of scientific photography, emphasizing those general principles which will apply no matter what may be the purpose of making photographs from the air. It is of course inevitable that whoever at the present time attempts a treatise on this newest kind of photography must draw much of his material from war-time experience. If, for this reason, the problems and illustrations of this book are predominantly military, it may be remembered that the demands of war are far more severe than those of peace; and hence the presumption is that an account of how photography has been made successful in the military plane will serve as an excellent guide to meeting the peace-time problems of the near future.

It is assumed that the reader is already fairly conversant with ordinary photography. Considerable space has indeed been devoted to a discussion of the fundamentals of photography, and to scientific methods of study, test, and specification. This has been done because aerial photography strains to the utmost the capacity of the photographic process, and it is necessary that the most advanced methods be understood by those who would secure the best results or contribute to future progress. No pretence is made that the book is an aerial photographic encyclopædia; it is not a manual of instructions; nor is its appeal so popular as it would be were the majority of the illustrations striking aerial photographs of war subjects. It is hoped that the middle course steered has produced a volume which will be informative and inspirational to those who are seriously interested either in the practice of aerial photography or in its development.

The writer is deeply in debt to many people, whose assistance of one sort or another has made this book possible. First of all should be mentioned those officers of the English, French and Italian armies through whose courtesy it is that he can speak at first hand of the photographic practices in these armies at the front. It is due to Lieutenant Colonel R. A. Millikan that the experimental work of which the writer has had charge was initiated in the United States Air Service. To him and to Major C. E. Mendenhall, under whom the work was organized in the Science and Research Division of the Signal Corps, are owing the writer's thanks for the opportunities and support given by them. A similar acknowledgment is made to Lieutenant Colonel J. S. Sullivan, Chief of the Photographic Branch of the Army Air Service, for his interest and encouragement in the compilation of this work, and for the permission accorded to use the air service photographs and drawings which form the majority of the illustrations.

The greatest debt of all, however, is to those officers who have formed the staff of the Experimental Department. To mention them by name: Captain C. A. Proctor, who was charged with our foreign liaison, and who acted as deputy chief during the writer's absence overseas; Captain A. K. Chapman, in charge of the work on optical parts, and later chief of our Rochester Branch; Captain E. F. Kingsbury, who had immediate charge of camera development; Lieutenant J. B. Brinsmade and Mr. R. P. Wentworth, who handled the experimental work on camera mountings and installation; Lieutenant A. H. Nietz, in charge of the Langley Field Laboratory of the Experimental Department; Mr. R. B. Wilsey and Lieutenant J. M. Hammond, who, with Lieutenant Nietz, carried on the experimental work on sensitized materials. A large part of what is new and what is ascribed in the following chapters to “The American Air Service” is the work of this group of men. Were individual references made, in place of this general and inclusive one, their names would thickly sprinkle these pages. It has been a rare privilege to have associates so able, enthusiastic, and loyal.

THE AUTHOR

NOVEMBER, 1919

CONTENTS

I. INTRODUCTORY

CHAPTER PAGE

1. GENERAL SURVEY 15

2. THE AIRPLANE CONSIDERED AS A CAMERA PLATFORM 20

II. THE AIRPLANE CAMERA

3. THE CAMERA—GENERAL CONSIDERATIONS 39

4. LENSES FOR AERIAL PHOTOGRAPHY 44

5. THE SHUTTER 68

6. PLATE-HOLDERS AND MAGAZINES 87

7. HAND-HELD CAMERAS FOR AERIAL WORK 95

8. NON-AUTOMATIC AERIAL PLATE CAMERAS 102

9. SEMI-AUTOMATIC AERIAL PLATE CAMERAS 116

10. AUTOMATIC AERIAL PLATE CAMERAS 124

11. AERIAL FILM CAMERAS 130

12. MOTIVE POWER FOR AERIAL CAMERAS 145

13. CAMERA AUXILIARIES 163

III. THE SUSPENSION AND INSTALLATION OF AIRPLANE CAMERAS

14. THEORY AND EXPERIMENTAL STUDY OF METHODS OF CAMERA SUSPENSION 179

15. PRACTICAL CAMERA MOUNTINGS 193

16. INSTALLATION OF CAMERAS AND MOUNTINGS IN PLANES 208

IV. SENSITIZED MATERIALS AND CHEMICALS

17. THE DISTRIBUTION OF LIGHT, SHADE AND COLOR IN THE AERIAL VIEW 221

18. CHARACTERISTICS OF PHOTOGRAPHIC EMULSIONS 227

19. FILTERS 239

20. EXPOSURE OF AERIAL NEGATIVES 247

21. PRINTING MEDIA 252

22. PHOTOGRAPHIC CHEMICALS 257

V. METHODS OF HANDLING PLATES, FILMS AND PAPERS

23. THE DEVELOPING AND DRYING OF PLATES AND FILMS 267

24. PRINTING AND ENLARGING 279

VI. PRACTICAL PROBLEMS AND DATA

25. SPOTTING 291

26. MAP MAKING 304

27. OBLIQUE AERIAL PHOTOGRAPHY 320

28. STEREOSCOPIC AERIAL PHOTOGRAPHY 329

29. THE INTERPRETATION OF AERIAL PHOTOGRAPHS 351

30. NAVAL AERIAL PHOTOGRAPHY 368

VII. THE FUTURE OF AERIAL PHOTOGRAPHY

31. FUTURE DEVELOPMENTS IN APPARATUS AND METHODS 383

32. TECHNICAL AND PICTORIAL USES 388

33. EXPLORATION AND MAPPING 401

I
INTRODUCTORY

AIRPLANE PHOTOGRAPHY