An Optical Illusion at Dunstanburgh

I often visit Craster and the area round about. It is one of my favourite places. Dunstanburgh interests me from the point of Northumbrian history and as an artist I love the play of light on the castle ruins and the constantly changing colours of the bracken and grass through the seasons.I have explored the area a lot as a landscape painter and from one point up on the heugh you can see an example of a classic optical illusion.

Dunstanburgh from the Heugh

When  you look at the horizon in this photo above  I believe that you will see that on the right the horizon appears to be somewhat higher than it does on the left of the picture. This isn't really the case as you can see where I have superimposed a grey  layer on the second picture with a  straight line running along the horizon.

And another view where the illusion is even more obvious.

The illusion is  presumably caused because our eyes/ brain is disturbed by the mass of the castle in the centre of the picture and cannot, so to speak, join the two parts of the horizon line. On the left there is the steep fall of the land below the Lilburn tower  which, I would say, adds to the confusion. The silhouette of the castle itself may be an additional difficulty.

The bent or broken line illusion was discovered in the 1860s by JC Poggendorf a physicist. You can learn more about this illusion here and in this PDF