If you have a large church with 6 big windows on the south and six on the north. Do you paint the north windows lighter that the south ones that have to withstand much stronger light?
How do you decided how much difference to paint them.
I did a glass painting of Mary who looks great in my north window, but fads to nothing in my south window.
Up here in the north the sun goes around the horizon, not over head. So East, South , West window get full sun in the summer. Only the south window gets any sun for an hour at Christmas. At noon, church time, the sun is consistently in the south.