Do great works of art transcend time and place? Of course. Still, it is possible to attribute many realistic paintings I see in museums and reproductions to a specific periods of time because of what we call "style" (regardless of the subject depicted.) While I have no doubt that materials, methods, and voluntary choices influence the aesthetic of these paintings, I do not believe that every decision on the painters part was objective. So yes, differences are an impediment to objectivity.
I believe that the camera's eye has influenced our perception of visual reality. How can one not be influenced by the aesthetic of the barrage of imagery we come in contact with through paper and electronic media? It's influence can be seen on many fronts in representational painting: framing, photographic finish, saturated colors and geometric composition come to mind immediately, and I'll be more than happy to give detailed examples if you'd like.
What's my point, and why does this matter? Knowledge lets you make informed decisions, and better paintings.
I think we might have to agree to disagree on this one.
