Sweet picture.

No need to try the alternate channel - ambient does the same thing in this case, and it gives you a dial instead of a colour to adjust brightness.
But can I see soft shadow on the background from the figure? Or is that just a darker area in the background image?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)