In this era of increasingly accurate 3D computer imagery, animators have come up against a problem known as the “uncanny valley” — after a certain point, the closer to accurate 3D imagery is, the creepier it becomes. The reason that it’s a “valley” is that it’s assumed that once we hit on absolute accuracy, it will no longer be creepy. I believe that assumption is unfounded. If we hit absolute accuracy, we would also hit the level of absolute creepiness. Human culture may never recover.
Humanity was in danger of hitting this uncanny point of horror at once before, during the Renaissance. At that time, painters and sculptors strove for the greatest possible accuracy, and the results are often startling, especially in the case of sculpture. Close-ups of familiar pieces like Michelangelo’s David reveal detail that is almost literally unbelievable.
Now for contemporary viewers, it’s the most natural thing in the world that all those sculptures are unpainted. Yet it’s now known that the reason for this is a historical accident. The Greeks and Romans painted their sculptures, but after many centuries, there was no apparent evidence of this fact. The Renaissance sculptors, in their passion to imitate classical models, thus left their sculptures unpainted.
There’s a certain irony in this fact, but there is also a saving grace — for imagine what would have happened if the Renaissance artists, with their passion for absolute imitation of nature, had actually combined sculpture and painting. A version of Michelangelo’s David that was painted as accurately as it is sculpted would, I submit, be utterly unbearable to look at. It would be too real. Only the abstraction of color allows the accuracy of the sculpture to provoke wonder rather than horror.
My proof for this is Bernini’s Rape of Proserpina, where the absolute accuracy of the form is so extreme that it can, at least for some viewers, overwhelm the abstraction from color and cross deeply into the uncanny valley. Where Pluto’s fingers touch her thigh, we believe we see real flesh, and the effect can either be appreciative disbelief — or revulsion.
An und für sich 
I wonder if there has been scholarship around this issue? I’m curious when the painting of sculptures came to an end. When I was in Paris over the summer, l learned that all the sculptures at Notre Dame were originally painted.
Most medieval church facades were even gaudily painted. Conques has some remaining paint. Here is Notre Dame at Amiens, believe it or not: http://marc-haegeman-photography.com/p983474479/h3965C89E#h3965c89e
In Spain some of the polychrome facades lasted until the 18th century, when they were finally whitewashed to accord with changing tastes. It’s amazing, however, how quickly all that was forgotten. When early modern Romans were just digging up ancient sculptures as a matter of course, they would scrub them to get rid of all traces of color. By the 19th century, people were actually unsure about whether or not ancient sculpture had ever been painted, and it was a matter of scholarly debate.
If it were absolute accuracy, would the sculptures move ever so slightly?
My sense of the uncanny valley is that it pertains most directly to moving “sculpture” i.e. animatronics and computer generated humanoid persona. As far as I’m concerned, Bernini, et al. completely cleared the uncanny valley with respect to stationary figures. Stripping color from a photograph doesn’t make it any less realistic, and painted sculpture looks less realistic than the unpainted version. If the Rape of Proserpina could move, it would look completely real.
Every sculpture wants to move.
Colorized photographs that are already famous in their black-and-white state have indeed seemed strange to many people, precisely because the black-and-white didn’t seem quite as real, and thus had an aura of seriousness or distance that feels awkward when the subjects suddenly resemble “real life.” Here are some examples — see if you feel this yourself:
http://sannadullaway.com/vs4t8ra5iho23yibtclg9kxrrvf7qk
Obviously a colorized Lincoln will be uncanny! I was actually waiting for the iconic kissing couple from WWII.
This is a pretty old trope isn’t it? Canova supposedly smacked down an admirer who said his sculpture was almost alive that “he did not want to create a wax work” – i.e he didn’t want it to be too lifelike, to be confusing (an effect waxworks achieve by coloured).
And Krauss, of course, made her bones in an essay on Greenberg’s monochroming of David Smith’s painted sculptures.