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Copyright © John Lindsay, 2015

GEOG*2420

The Earth From Space


Filters and Photographic Film



John Lindsay
Fall 2015

Readings

Jensen Chapter 4, pg. 107-124

Don't worry about the formulas on page 116.

Filters

Filters
Filters (source: Jensen, 2006)

Photographic Film

The density and size of silver halide crystals affect film speed and spatial resolution. The larger the crystals, the higher the sensitivity but the coarser the resolution (i.e. reduced sharpness).

Film silver halide crystals (source: Jensen, 2006)

Film Types

  • Black & white orthochromatic—sensitive to blue and green light (to 0.6 μm)
  • Black & white panchromatic (to 0.7 μm)
  • Black & white infrared (to 0.9 μm)
  • Standard (normal) colour
  • Colour infrared (CIR)
Film types
(source: Jensen, 2006)

Film Types

Film types

Sensitivity of Selected Black & White Films and Printing Paper

Sensitivity of film types
(source: Jensen, 2006)
Sensitivity of film types

Spectral Sensitivity of Normal Colour and Colour-Infrared Film

Sensitivity of film types
(source: Jensen, 2006)
CIR film
(source: Jensen, 2006)
CIR film
(source: Jensen, 2006)

Advantages of pan and normal colour film

  • More natural to the human eye than infrared
  • More detail is apparent in areas of shadow
  • Better spatial resolution
  • Better penetration of water bodies

Advantages of B&W Infrared and CIR

  • Better penetration of haze
  • Emphasizes water and moist areas (good for mapping water bodies)
  • Good differentiation between hardwoods and conifers
  • Sick, dying, and stressed vegetation is more easily detected, especially on CIR

Example of spectral signatures for foliage across the visible and near IR

spectral signatures for foliage
(source: Unknown)