Hi Bjorke

My first year in photo-college 1973, we were forced to do a negative ring a round and a paper ring around that looks alot like this article, I did not have a clue at the time the purpose of this experiment.
I think if I did one now I would have a better appreciation on push and pulls with over , under and normal exposures.
We also were forced to do a colour ring around from nuetral density and colour and the results are quite amazing.
Still do colour ring arounds with interns here and I will force them to do a black and white ring around after looking at this article.