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CU-Boulder GEOG 5093 - CAMERAS

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GEOG/GEOL 4093/5093 344. AERIAL AND SPACE PHOTOGRAPHYMore than 100 different models of aerial film cameras arecurrently in use. They can be divided into the following fourcategories4.1.1. Single-lens frame camera• Most common camera in use today• Used for mapping ⇒ metric or cartographic camera• Extremely high geometric image quality• Film size commonly square 230 mm• Wild RC-10 (airplane)• Large-Format Camera (LFC), Metric Camera (space)4.1.2. Multi Lens frame camera• Photographs taken from same object with different filterand film combinations• Multi-band photography ⇒ spectral information forclassification4.1.3. Strip camera• Record images by moving film past a fixed slit in thefocal plane• Film is passing over the slit at the same speed of themoving image4.1.4. Panoramic camera• Ground areas are covered by either rotating thecamera lens or rotating a prism in front of the lens• 180° scan angle ⇒ large geometric distortion4.1. CAMERASGEOG/GEOL 4093/5093 35CAMERASGEOG/GEOL 4093/5093 364.2.1. Film exposure• F/number = f/d f = focal length (mm); d = effective lens diameter (mm)4.2.2. Viewing angle• Angular field of view (AFOV)• Vertical air photos• Oblique air photos• High-oblique air photos4.2. CAMERA OPTICSGEOG/GEOL 4093/5093 37Conventional lenses have a short-wave cutoff at 350 nm (quartzlenses at 300 nm)Spectral sensitivity of B/W films4.3.1. Blue sensitive film• Affected by x-rays, gamma rays, UV, violet, and blueradiation• Insensitive to longer wavelengths4.3.2. Orthochromatic film• Blue and green sensitive4.3.3. Panchromatic film• Red, green and blue sensitive• Extended red sensitivity to reduce atmospheric haze (720nm)4.3. FILMSGEOG/GEOL 4093/5093 38FILMS4.3.4. Infrared film• sensitivity in addition to panchromatic is extended to 900nm4.3.5. Color film• at least three photosensitive layersGeneralized diagram of a normal color film. UV radiation is cutby haze filterGEOG/GEOL 4093/5093 39Object Panchromatic InfraredSnow White WhiteClouds White WhiteSky Medium gray BlackClear water Dark gray BlackSilty water Light gray Medium grayDeciduous foliage Dark gray WhiteConiferous foliage Dark gray Medium grayAutumn foliage Light gray Light grayWhite sand (dray) Light gray Light grayWhite sand (moist) Medium gray Dark grayRed sandstone Medium gray Light graySwamp Dark gray BlackAsphalt Dark gray BlackConcrete Light gray Medium grayObject Normal Color Color InfraredSnow White WhiteClouds White WhiteSky Blue BlueClear water Blue or green Black or dark greenSilty water Red or brown Light blue or greenDeciduous foliage Green Bright redConiferous foliage Green Brownish redAquatic vegetation Green PinkCitrus trees Healthy Green Red Previsual stress Green Pink Late stage of stress Yellow WhiteRed sandstone Red Yellow or greenAsphalt Black Black4.4. OBJECT SIGNATURES PAN/INFRA, CO/CO-INFRAGEOG/GEOL 4093/5093 404.5.1. Film resolution• Defined as lines per millimeter• Resolution depends on target contrast• High contrast target large density difference betweenbright and dark, and visa versaKodak Panchromatic films• High contrast: 400 lines/mm• Low contrast: 125 lines/mm4.5.2. Ground resolutionRg = (Rs f ) / H;Rg = ground resolution,Rs = system resolution (film – camera – lens)f = Focal length (mm)i.e. 40 lines/mm x 300 mm / 6000 m = 2 lines / m4.5. RESOLUTIONGEOG/GEOL 4093/5093 41Kodak Wratten 12: yellow filter, filters UV and blue,decreases atmospheric hazeKodak Wratten 25: red filter, absorbs UV, blue and green⇒ high altitude operationKodak Wratter 89: only NIR will be recorded - true infraredphotographs, excellent hazepenetration qualities4.6.


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