When you think art reproduction, you probably think of something that looks almost identical to the original piece, but as Martin Wattenberg and Fernanda Viegas show in The Art of Reproduction, factors such as color and size can vary a lot:
Curious just how far reproductions stray from each other, we began an investigation... For a set of famous artworks, we downloaded all the plausible copies we could find. Then we wrote software to reconstruct each artwork as a mosaic, a patchwork quilt where each patch comes from an individual copy.
The above is a mosaic of reproductions of 21 Tears by Man Ray, and as you can see, the colors across reproductions span grayscale to green.
Here's the reproduction for 22 Saints and Angels by Caravaggio. Again, notice the difference in shades. Edges aren't straight because different reproductions crop the original at different points.
See the full gallery here.