How Portrait Photography Helps My Drawing

The scariest assignment so far in the faces class I'm taking has been this one because we're supposed to draw realistic faces. Which means there's a high degree of opportunity to fail. I'm pretty happy with these two portraits. Are they perfect? No. But, if you asked me last week if you thought I could draw anything this good, I would have said, "Heck no!" So, I'm pleased with my efforts.  The portrait on the left is based on my mother-in-law's bridal portrait.  The one on the right is based on this photographic portrait I took of a local activist:

It's my favorite of the two. I think that having spent time on improving my portrait photography is helping my attempts to draw faces. When photographing portraits, the key is to find enough light to have catchlights in the eyes and to have a natural expression.  I think the same thing is true in drawn faces.  I try to put "catchlights" in the eyes, and I have found that using a model with a good expression really helps me draw a more expressive face. 
It's a happy coincidence that my efforts to improve in one art form have delivered dividends in another one. Has this every happened to you?