Electric, drive for cameras, 116, 119, 123, 145, 149 generator operated by motor, 146 motor, characteristics of, 151, 156 motor, service, 163 Elevation possible to detect in stereoscopic views, =340= Emulsions, photographic, characteristics of, =227= Enlarging, 45, =279=, 283 camera, 283 Enlarging versus contact printing, 59 Exhaustion of developer, 259 Exploration, use of aerial photography in, 401 Exposure, data charts, 250 distance between for mosaic maps, 307 distance between for stereos, 336 estimation of, 248 limitations to, 247 meters, 251 meter, Wynne, 251 of aerial negatives, =247= relation between motion of plane and, 68, 185 under, period, 230 Field, angular, of lens, 57, 302 flatness of lens, 56 Field laboratory, mobile, 268 Film cameras, 43, =130=, 134 Brock, 138 Duchatellier, 131, 136 F type, 134, 171 G.E.M., 138 German, 64, 76, 139, 317 K type, 142, 203, 214 Film, celluloid, 130 backed, 133 changing in the air, 137, 144 color sensitiveness of, 237 cut, 275, 278 development of, 130, 272 drying, 131, 276 means for holding flat, 130, 131 relative performance of compared to plates, 237 satisfactory kinds for aerial work, 238 shrinkage, 237 Filters, 15, 58, 106, 174, 224, 233, =239=, 241, 243 effects secured by use of, 241 Filters, gelatin, 244 glass, 245 holders for, 67, 106, 224 ratio, 240 Fixing bath, 262 Flaps, auxiliary to shutter, 80, 84, 85, 98, 99, 101, 119 to protect lens, 214 Flash lights, 18, 386 Flying boat, 374 Focal length, relationship of lens characteristics to, 55, 57 requirements for, 39, 42, 58, 61, 103 Focal plane, 50 shutter, 70, 71 distortion by, 74 performance of, 86 types and representative, 80 Focus, depth of, 44 effect of temperature on, 41, 65 fixed, in aerial cameras, 40 ground and air, 65 Focussing, automatic, 284 by parallax, 65, 66 Fog, atmospheric, 224 photographic, 237, 258 French aerial photographic practice, 45, 46, 283 Friction disc speed control, 136, 159, 160 Fuselage, 21, 87 shape and size depending on type of engine, 23 Future of aerial photography, =383= German aerial photographic practice, 63, 103, 209 Glass, optical, used in lenses, 44 Gloves, handling apparatus through, 41, 89 Governor for camera speed, 159 Graphite, use of to prevent static discharge, 134 Gravity, action of in aerial cameras, 41, 112, 115, 119 center of, should not change in cameras, 125, 207 change of center of, in magazines, 92, 112 depended on in magazines, 88 handles best at center of, 96 pseudo, in moving vehicle, 188 support at center of, 182, 203 Ground speed, 27, 307 indicator, 311 Guide-books, illustration of, 15, 392 Guides for inserting magazines, 41 Gyroscope, 189 Gyroscopically controlled instruments, 29, 174, 192, 312