If you have an interest in photography, painting realistic miniatures or backdrops, and have a spare 41 minutes, I strongly suggest you watch this video. The last three minutes are especially fascinating.
In this video Professor Philip Steadman, UCL Bartlett School of Environment, Energy and Resources, provides a "proof" of his theories on how the famous Dutch painter Vermeer used a modified camera obscura to paint his "photorealistic" scenes.
When I was in graduate school in mechanical engineering, I had one unrestricted elective class. I took photography. In that class we made a camera obscura in a dark room in the old armory at MIT. It was really fun to watch the outside scene projected on the walls of the darkened room. But the room was too dark to paint in. This video shows how Vermeer probably developed the camera obscura even further to create a device that could record a scene and allow enough light to make a painting. There is a documentary film mentioned in the video, "Tim's Vermeer," that I have not seen, but plan to at some point.
Prof Steadman also makes a point that there are no out lines in Vemeer's artwork. I have noticed a similar effect when working with Photoshop. When you reduce an image to colored dots (pixels), and look at the dots in a magnified way, you can see this clearly. You'll even note that the areas were colors meet are not sharp, but tend to blur into each other. Being aware of this effect makes compositing images in photoshop more realistic. Sometimes, you have to add blur to an image to make it more realistic.