JORNEX'99 Photos : BRDF effects in Grassland at JER
JORNEX Bouteloua Grassland Site
Note the change in the proportion of soil visible from the top to the bottom
of each images - you don't have to be a genius to see that less soil is
visible at the top (where the view zenith angle is high) than at the bottom.
There is a small degree of vignetting in these images (darkening away from
the centre); however, the effect of changing illumination from the forward-scattering
to backscattering directions is clearly more important - more shadowing
in the top photo! The centre of the images is close to the principal plane
(the plane made by the sun, the target and the viewer); the shadow of the
photographer points straight ahead. Note that these images were scanned
at the same time and the camera made no automatic exposure adjustments
- the brightness and contrast is therefore a function of the camera optics
and the single brightness/contrast setting of the scanning software (the
images were scanned simultaneously).
Top : Looking towards the sun (forward-scattering); Bottom : Looking away
from the sun (back-scattering); Solar zenith angle 55 degrees) :
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