So I had this idea to photograph a certain type of building at a certain time of day. About a hundred years ago they passed a law here requiring all buildings to have a beveled corner. I believe it was to improve visibility for automobiles at intersections. The law only applies to the ground floor, however. There are a lot of these functional apartment buildings from the 1960s where losing those few square meters was simply economically unacceptable. The result is a sharp corner above the diagonal. If the building faces the sun and if there's no opposite building casting a shadow [VERY big ifs], then you get this triangular shadow. I've been noticing this for awhile. My
first photo of an ochava shadows dates from August 2008. Finally a few months ago I decided to make a project out of it. With a list of corners I'd already scouted out, I went on sunny days and photographed them with my 4x5 camera. The timing can be tricky. This corner here was the very first one I did. I arrived about 2 hours early, as you can see from the progression below:

When the moment comes I have to hope nobody parks illegally on the corner or that some cloud appears from nowhere to block the sun.