Drew has the right idea about PhotoFocus. It is a natural way to see with the whole mind. There is an interesting corollary that I use to get people into it: Hold your thumb in front of you where you would hold a book for reading and look only at the thumbnail. As you do this, stand up and walk around for a short while, among people, around furniture, etc. then find your way back to your chair. You'll discover that you can navigate perfectly well and you don't bump into anything. You have developed PhotoFocus to allow your brain to process everything around you without the need to consciously focus on any of it. You focused on a near point to have PhotoFocus on all other information.
To develop PhotoFocus for a book in front of you (a near point), have your vision beyond the book and notice a point further away that you can fixate upon. There you have it.
Blip or no blip, stereogram or no stereogram, the goal is to allow the brain to do its preconscious processing work. You accomplish this by sending your conscious attention to something other than what your brain must process.
The reason many people do not see a blip or a 3D sterogram is eye dominance. Your brain is still taking all the information in, but your conscious mind is oriented only to the information coming into the dominant eye. This poses no problem for PhotoReading.
As an artist, my wife uses PhotoFocus to preceive anything around her. She "PhotoReads" a landscape, a room, a wall, you name it. Others use this state when they walk into bookstores and libraries. Try it and ask your brain, "What is here that I need to explore in more detail?"