Viewers only.

  

“You have to let the person who will look at the picture - provided that he isn’t an ass - always walk along that visual path for himself. We must always remember that a picture is made up of the person who looks at it. This is very, very important. Maybe this is the reason behind those photos that haunt me and that haunt many people as well. It is about the walk that one takes with the picture when experiencing it. I think that this is what counts. One must let the viewer extricate himself, free himself for the journey. You offer the seed and then the viewer grows it inside himself. For a long time I thought I had to give the entire story to my audience. I was wrong.”

Robert Doisneau, in Dialogue with Photography. Interviews by Paul Hill and Thomas Cooper, Drew Lewis Publishing, New York, 1998.

While the above quote would initially seem obvious for those partial crops of well known items where the viewer fills in the details, and the abstract macros where the meaning is left entirely for the viewer, speaking from experience I know that all it takes is a browse through your favourites on flickr to understand what Robert means.