"Photography can only represent the present."

I'm not sure I understand this quote because it goes on to say that once the photo is taken the subject becomes part of the past.  This part I agree with, but wouldn't that make it more correct to say that photography can only represent the past?  It represent things that were, that used to be.  It used to represent something that was the present, but now what is picture is in the past.  I think I'm confusing myself now.