It looks like there is a too-weak light on the background and the image can't tolerate much Shadow/highlight at all before the boy's face gets too light and the hair looks washed out. He is a great looking kid.
There was no back light, I was just testing the lens with my son using two lamps only, but I loved his expression so I decided to post It.
Traveler I did not know the size limit so I play it on the safe side, but here is a bigger version.