Looking at shadows in paintings

I'm not doing too much urban sketching these days, but a lot of work on my watercolour and painting skills. This is me going analog - using old projection acetate transparent sheets to place over some paintings with interesting shadows and writing down all the wonderful things that I see happening. I won't be sharing the originals, as they are in books by famous watercolour artists, and I respect their work too much!

This one is by Tom Hoffmann, and it's blowing my mind - he's observed and painted all these amazing cast shadows and reflected light, thinking about temperature and value and getting everything so perfect!

The next two are by Alvaro Castagnet, very different style, but also a master of light and shadow. Again, he uses warm and cool shadows to draw your eye, and reflected light in such a subtle way that it just appears natural, until you think "hold on a second, this was so deliberate, there was no luck or happy accident here!"