Everything everyone has said good and right,… but you said “...to increase its realism” your render is fine! And real! NOW before people start piling on; you said realism not photo realism; BIG difference. Some where on the daz forums there is a whole large (many post) topic on this, and one person who can really do great “life-like?” photo realism renders.

In life ‘realism’ everything is in focus. Your eyes focus, a camera is even worse, the ‘realism’ you(or other people) appear to want is the defects of the human eye and worse the camera. Like I said there is one person (in  the daz forums) who does the defects really good, flash and all. Photographers have all always wanted to go the other way where everything is in focus and then you can back and if you want ‘get creative’.

When I hear people say they want photo realism I know what they want, I don’t think they know what they want/mean.