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Figure 1 is an infrared (IR) photograph, taken at Banff National Park of Canada in the morning of September 17, 2008.
It was a sunny but hazy day, which can be seen from the color picture (Figure 2) that I took with a Canon EOS 20D at approximately the same time and the same spot.
It is believed that haze appearing in both urban and rural environments is caused by particulates suspended in the air. A direct effect of light scattering through the haze particles on aerial or terrestrial photography is a loss of contrast in distant subjects. A hazy weather might be a chance for producing a creative image, but in general, it is not a particularly desired condition for landscape photography.
In scientific terms, haze particles are spectrally selective. This means that short wavelengths (e.g., violet, 380 - 450 nm) in the visible spectrum (approximately 380 - 750 nm) are scattered more, and long wavelengths are scattered less. As we know, near IR light employed for photography ranges from about 700 nm to 1200 nm, depending on specific IR filters being used. Consequently, shooting IR with longer wavelengths can cut through the haze, making a hazy scene much clearer with sufficiently rich contracts.
The picture shown in Figure 1 was taken with a B+W 093 IR filter and a dedicated digital IR camera. The B+W 093 filter has a cut-off wavelength of 850 nm. As a result, it blocks the entire visible spectrum and has a stronger IR effect than the less visually opaque filters. In comparison with the color photo of the same scene, the details of the mountain rock structures are revealed quite clearly. Also, the sky and the lake have become much darker, and the trees become much brighter. All this is expected because the former absorbs the IR light and the latter reflects the IR light effectively.
In summery, an IR camera can see more clearly than the human eye on a hazy day and it is fun to shoot IR landscape during such time. You may bring back home some nice IR images while the regular color or traditional black and white pictures appear to lack enough contrast under the same atmospheric conditions.
Figure 1 Reflection at Two Jack Lake
Figure 2 Hazy Mountain Lake
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