We use a lens to see.  Like a magnifying glass for example.  To see close up.  I have in my library the one-volume addition of the Oxford English Dictionary, that is, a 20+ volume work reduced down to one volume.  The one volume has 2371 pages, and each page has 9 pages of the 20+ volume work reduced to fit.  The one volume work comes with a magnifying glass.

Or like a telescope.  During the 2010 football season, I was watching an NFL game late Sunday afternoon.  At halftime, the announcers said they wanted to show something unusual.  One of the cameramen had been getting his camera ready for the telecast, and to check out his zoom lens, he focused on the moon, and then zoomed out past the moon until finally (as his camera test had been recorded and now millions of people were watching on television) we could see on television the rings of Saturn.  It was an amazing few minutes.

And so the idea of a lens has become a metaphor for seeing things, for bringing them up close, for bringing things into focus.  A lens helps us understand.

A photographer uses two lens to make a photograph, the lens of his or her camera and the lens of her or his eye.  We look through the photographer's lenses to see and even seeing is a metaphor for understanding.  There is a possibility that a well seen photograph can affect our own vision of the world.  A well-seen photograph could perhaps provide a better understanding of the world within which we all live, an understanding of what we may not have seen before.