Photography as "Mirrors" or "Windows"

I've been reading "Strange Hours: Photography, Memory, and the Lives of Artists" these last few weeks. I found an interesting thought from John Szarkowski:

What makes this more interesting for me is that my "Faribault County" work from 20 years ago would fit as a "window," but my more recent "4 a.m." work is definitely a "mirror." I don't know what that means, but it's made me stop and think about my own art making...

Framing an Image

To quote out of context is the essence of the photographer's craft. His central problem is a simple one: what shall he include, what shall he reject? The line of decision between in and out is the picture's edge. While the draughtsman starts with the middle of the sheet, the photographer starts with the frame.

The photograph's edge defines content.

It isolates unexpected juxtapositions. By surrounding two facts, it creates a relationship.

The edge of the photograph dissects familiar forms, and shows their unfamiliar fragment.

It creates the shapes that surround objects.

The photographer edits the meanings and patterns of the world through an imaginary frame. This frame is the beginning of his picture's geometry. It is to the photograph as the cushion is to the billiard table.

- John Szarkowski's words to open the chapter titled "The Frame" in "The Photographer's Eye."
(This was the catalog for an exhibition at the MoMA in 1964.)