Illusion by illumination
deutsche Version

The image seen here on the right may remind the observer to look at things from more than one side. It seems to be a bird's view of a hill lit by the low sun while the surrounding plain is in the shade, with erosion furrows running down the steep slopes, and with the remains of an ancient hill fort on the plateau on top, enclosed by decaying walls.

calamiteBy turning the picture, something quite different suddenly appears, which seems to be a weathered statuette of a saint in a vault adorned with ray-like grooves.
Really it is neither. It is a Lower Permian calamite fragment suitable for small talk about illusion and reality in a confusing world where hills may be not real but apparitions can be touched.
To be serious, the present illusion is only another manifestation of the well-known fact that photographs of less-common objects should be taken with light coming from above left in order that the shadows produce the proper 3D-effect. With the picture turned upside down, as shown above, the light comes from below right, which makes all the difference between the visual impressions.

The brain is not accustomed to pictures taken with light from below right and therefore processes them, in the absence of other clues, as if the light had come from above left, thereby creating, in the present case, the image of a hill instead of a depression. The phenomenon is particularly striking when a print of the picture is turned slowly until the brain suddenly switches to the alternative image.
More often than not, photographs in publications are presented with such orientation that they are misleading.
For the palaeobotanical aspect of this fossil see
Fossil Wood News 13 

Sample: found during the IOPC VIII conference (2008) on a field trip to Schallodenbach, Saar-Nahe Basin, Germany.

H.-J. Weiss   2012

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