Well, if I could definitively answer that question, I would have quite the following.
Alas, I can't answer it. That's why we take photo after photo after photo and never get that perfect shot.
Calling his name will not get him to look.
Singing songs will not get him to lift his head.
Ringing bells or clapping your hands will not get a face to the camera.
Pleading and begging will not motivate him to open his eyes or focus them in the same direction.
The same is true for getting him to crawl. Who wants to move when you can't see where you're going? We've tried all the same noisy tricks to motivate him to want to move forward, to no avail. However, give him a piano and he becomes Tom Hanks in Big.
Wait til Ms. Diane comes for therapy today. We have a lot to show her!