 He also realized that images are "painted" inverted and reversed on the retina of the eye and figured that this is somehow corrected by the brain.In 1607, Kepler studied the sun in his camera obscura and noticed a sunspot, but he thought it was Mercury transiting the sun.In his 1611 book "Dioptrice", Kepler described how the projected image of the camera obscura can be improved and reverted with a lens.