Atmospheric
Optics
In Clover
A shadow hiding opposition effect in a field of clover. Imaged by Alexis Tourrette. The camera shadow is directly opposite the sun. In that direction the shadows of the clover leaves are hidden behind the leaves themselves. The shadow free area appears brighter than its surroundings. Image ©Alexis Tourrette, shown with permission
The shadows are towards the antisolar point.
Each leaf, represented at left by a green circle, casts its shadow directly opposite the sun.
The eye, closer to the field than the sun, views the shadows at a wide range of angles. In the direction opposite the sun it sees the leaves hiding their shadow. Farther and farther from the antisolar point the shadows become more and more visible.
Here the shadows are easily seen, on sand or a distant field the reasons for the opposition effect are less obvious.
Near the antisolar point there are hardly any shadows and the area is on average brighter for the lack of them.
