Foto

This picture was taken on the descent from Ebenalp to Wasserauen. The shadow is from myself, whereas the shadows of the people standing next to me were not visible.

The effect is called Brocken spectre (Brockengespenst):

"The "spectre" appears when the sun shines from behind a climber who is looking down from a ridge or peak into mist or fog. The light projects the climber's shadow forward through the mist, often in an odd triangular shape due to perspective. The apparent magnification of size of the shadow is an optical illusion that occurs when the observer judges his shadow on relatively nearby clouds to be at the same distance as faraway land objects seen through gaps in the clouds, or when there are no reference points at all by which to judge its size. The shadow also falls on water droplets of varying distances from the eye, confusing depth perception. The ghost can appear to move (sometimes quite suddenly) because of the movement of the cloud layer and variations in density within the cloud.

The head of the figure is often surrounded by the glowing halo-like rings of a glory, rings of coloured light that appear directly opposite the sun when sunlight is reflected by a cloud of uniformly-sized water droplets. The effect is caused by the diffraction of visible light." from Wikipedia