Chapter 23. Depth of Field: A Survey of Techniques

https://developer.download.nvidia.cn/books/HTML/gpugems/gpugems_ch23.html

what is depth of field?
depth of field is the effect in which objects within some range of distances in a scene appear in focus, and objects nearer or father than this range appear out of focus. depth of field is frequently used in photography and cinematography to direct the viewer’s attention within the scene, and to give a better sense of depth within a scene. in this chapter, i refer to the are beyond this foal range as the background, the area in front of this range as the foreground, and the area in focus as the mid-ground.

the depth of filed effect arises from the physical nature of lenses. a camera lens (or the lens in your eye) allows light to pass through to the film (or to your retina). in order for that light to converge to a single point on the film (or your retina), its source needs to be a certain distance away from the lens. the plane at this distance from the lens is called the plane in focus. anything that is not at this exact distance projects to a region (instead of a point) on the film. this region is known as the circle of confusion (CoC). the diameter of the CoC increases with the size of the lens and the distance from the plane in focus. 透镜越大，或者距离聚焦面越远，那么CoC的直径越大。because there is a range of distances within which the CoC is smaller than the resolution of the film, photographers and cinematographers refer to this range as being in focus; anything outside of this range is called out of focus, see below:

in computer graphics, we typically project onto your virtual film using an idealized pinhole camera that has a lens of zero size, so there is only a single path for light to travel from the scene to the film. so to achieve the depth-of-filed effect, we must approximate the blur that would otherwise happen with a real lens.

为什么人眼看到的是倒立的像，但是确是正立的？
http://k.sina.com.cn/article_2183122304_821fcd80001009o7h.html