I had to re-read it a couple of times but I finally got it.
The photographer's camera is like an extension of what he was viewing. So he views the living as bad while the corpses as beauty. Also if you look at the photographs, it shows all the corpses being held up by the members of the association. Yuki's 'same as me' could be also viewed that she also performed suicide with her artistic death painting which is the same feeling the photographer has. The members of the "Hiking Enjoyers Association" enjoy viewing a person's last moments and possibly help push people further to suicide.