Color Shift with Aerial Photographs
Regular color film |
Infrared film |
What you see above are two aerial photographs of the same college campus. The left photo is taken with regular color film and the fields surrounding the stadium are grass. The floor of the stadium appears to be the same color as the surrounding fields - and they are both green - but the stadium field is actually astroturf, not living vegetation.
The photo on the right is taken with infrared color film and shows a color shift. The grassy fields are now red (color shifted from INFRARED wavelengths to shorter red wavelengths). The red roofs of several buildings in the left photo show up as yellowish in the photo on the right (color shifted from red wavelengths to shorter yellow wavelengths). Note, however, that the stadium field does NOT shift to red. It is hard to see any color there at all (but in reality the blue-green astroturf should be color shifted to much shorter wavelengths - bluish). Because the astroturf is so dark in the left photo, you don't see much color in the right photo either.
Note finally that black on the regular color film photo shows up as black on the infrared and white on the visible photo shows up as white. But notice the main highway on the right side of the photo. It is actually asphalt (real color gray). In the INFRARED photo, the gray is color shifted to a gray-blue. This is why urban areas often look blue on satellite images - because of all the asphalt and gray roof shingles.