Haven't all paintings and sculptures throughout history derived much of their strength, if not all of their strength, from an intimate connection with reality, as perceived by the viewer?
No, not really. From a very early time -- the early Egyptians -- it was recognized that art almost always contained a variety of manipulations that removed it from reality. These manipulations could be either cultural or psychological, or both. (Google "Ahkenaten art.") In fact,in some eras, the Egyptians simultaneously made highly realistic art, somewhat abstracted art, and highly abstracted images derived from natural objects and used as hieroglyphic symbols -- so they had a full panoply of artistic styles and abstractions all in the same era, just as we do. They knew perfectly well that people didn't have both eyes on the same side of their head...
The thing that gave photography its power, right from the start, is that it in some way *removed* psychological and cultural manipulations. Artists of wildly different styles and temperaments could set up a camera in front of a landscape, and shooting one-after-another, take essentially identical photographs. They couldn't do that in their painting, nor would they want to. The photographic artist still selects the image he/she wants, but the raw image itself is firmly attached to an exterior reality, rather than the interior psychology of the artist. As far as I know, the very first photo that we have is a kind of landscape -- it shows the corner of a building. Any artist of the time (first half of the 19th century) could have made a better image of the same thing -- more realistic, correct color, etc.
So why go to photography at all? Because when it came to the most difficult images -- portraits -- the painter simply couldn't match them for flat, uninflected realism. This is the essential element that gives photography its power: the camera doesn't fix anything, doesn't look away, doesn't react to the cultural or psychological state of the artist. The camera simply takes an image. Because of that, photography has a certain credibility with viewers. All kinds of things can be done to a photo after it's taken, but those erode the credibility, rather than enhance it. For example, before we had color film, we had colorized prints. Yet, I've never seen a colorized print that appeared to me to present a higher degree of realism than a black-and-white. With a black-and-white print, I *know* that red and green may show up as the same shade, and I accept that, because that's all a black and white representation can do. Once a print is colorized, though, you begin to ask, "Really? Was the sky really blue and not gray? Was the grass really deep green, and not yellow-green?"
When a painter paints a portrait of somebody he knows to a certain degree, he has in his mind all of the different expressions of that person's face, as well as the way the person talks, his sense of humor, and so on. All that is taken into account in the process of painting. A camera simply makes an image -- the sitter may have hairs sticking out of his nose, may be haggard from a restless night, may have a pimple on his forehead, and the camera just doesn't care. A painter always does, and what he puts in or takes out is a matter of psychology and culture, a matter of choices. Many portrait artists today use photography to reinforce particular aspects of a portrait that they may have difficulty capturing in a live session, and in my opinion, to the extent that they do that, the deader the image becomes. Painted portraits, IMHO, require the psychology, culture and hand of the artist to be foremost, because that's where painting's strength is; a photographic portrait needs to push as close to an objective realism as possible, because that where the photographic strength lies.
