Depth of Field
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Depth of Field and the Eye
If you have 20/20 vision, you can see all focal planes from 20 feet away (your score is 20/20). In a camera, depth of field is achieved by controlling where the focal point hits the image sensor on a digital camera or the film in a film camera. In depth of field, the focal point hits right on the image sensor.
This is much the same as an eye with 20/20 vision. In an eye with 20/20 vision, the focal point of the light passing through the pupil hits the optic nerve. Therefore, there is no distortion in the image (no distortion in what you see).
This is much the same as an eye with 20/20 vision. In an eye with 20/20 vision, the focal point of the light passing through the pupil hits the optic nerve. Therefore, there is no distortion in the image (no distortion in what you see).
A picture is said to have shallow depth of field when the focal point is in focus, but the background and/or foreground is blurred. This technique is used a lot in portrait photography.
There are a couple ways to achieve shallow depth of field in your pictures, as follows:
There are a couple ways to achieve shallow depth of field in your pictures, as follows:
- Use a large aperture, f/5.6 or lower.
- Use a zoom lens.
- Bring your focal point close to you and the background far away.
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 optic nerve, crosses, and then lands on the optic nerve.
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 optic nerve, crosses, and then lands on the optic nerve.
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) or both.