On 14 Jan 2009 at 9:43, tim rolls BT wrote: > Hi Richard, > > I haven't got my physics head on this morning, but would this be > anything to do with the fact that many painters used a sort of camera > obscura device to project the model onto a canvas, then did a quick > sketch round the projected image, I can never get my head round > whether the image just inverts vertically or swaps L-R as well. > > Tim > ----- Original Message ----- >
Hi All, I had the same thought, but I came to the conclusion that image swaps top to bottom and left to right leaving the image unchanged. If it hadn't, all the paintings would have looked 'wrong' and clock faces etc would have given the game away. ---------------------- For those who have been taught symmetry operations. A mirror causes a mirror transformation (obvious). A pinhole is a centre of inversion. Thes are technical terms and I refuse to start a discussion on Symmetry and Group theory on this list. It would beo off-topic. ---------------------- Barry To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
