SnagIt said:So your new sigma is for portrait. I join the crowd to chime in too.
IMHO this is overall a good photo. A few things can give the photo some punch such as:
1. crop out the background more since it doesn't contribute much to the photo. If not can consider adding vignette
2. get closer / crop tighter for the face if you want to focus on the smile. Center is fine i think. Like this
Just a quick comment on your example. Your portrait can benefit greatly if you take one or two steps to your left. That angle will move the dark mess away from the side of your boy's head. Also a slightly off center composition will look a lot better too, especially in landscape orientation.