sdof+and+eye

=Shallow Dept of Field and the Myopic (nearsighted) Eye=

If you're nearsighted like I am, you can see things close in focus, but the background is not in focus. Sound familiar? Myopia (nearsightedness) is the result an eyeball that is not perfectly round, it is longer than it is tall (like an egg on its side). The result of a myopic eye is that the light traveling through the pupil meets in front of the retina, crosses, and then lands on the retina. Basically, the focal point is in front of the retina instead of on the retina.


 * [[image:phsc-incom/myopic_eye.jpg width="560" height="428" caption="See how the image or light focuses in front of the retina?"]] ||

Shallow depth of field is the same thing as myopia. To achieve the effect, we change where the image (or light) focuses before it strikes the image sensor in a digital camera or the film in an analog (film) camera. To change where the image focuses in the camera, we increase the aperture size or increase the focal length of the lens (zoom). **Basically, we have to make your camera near sighted.**


 * [[image:phsc-incom/Camerasdof_copy.jpg width="643" height="529" caption="Notice in this illustration how the light crosses (or the focal point) is in front of the film (or image sensor in a digital camera)? That's where everything is in focus. As the light travels to the film, it becomes out of focus, resulting in a picture that has shallow depth of field.  Digital works exactly the same way; instead of film light hits the image sensor.  By changing the focal length, we've changed the shape of the camera's "eye" (we made it near sighted.."]] ||