as far as I understood, it is a very simple and straight forward thing to do:
when you hold the book while you're PhotoReading, you normally have it right in front of you,

and for getting an exact photographic memory of the text/pages, you move the book to the left, and PhotoRead the text in that position.

(I just named what I heard of as ‘shifting to left’ technique, I don't know whether it has a name of its own or not.)

I would be very interested in knowing
more about this myself. (Probably Pete and others are familiar with this.)

Maybe I should just try it right now, and see what results I can get!

Pia