Camera Techniques: Depth of Field
Depth of field is a photography term that describes the area of a photo that remains sharp while the rest becomes blurry. A very narrow depth of field is useful for isolating a subject and making it pop out, while a very wide depth of field is used in landscapes when the photographer wants everything in focus. Regardless of your goal, controlling depth of field is an important technique to learn to improve your photography.
Controlling depth of field
There are three variables that determine your depth of field: the aperture of the lens, the lens focal length, and the distance between the camera and the subject. In general, a wide-open aperture (a low F/number) will produce a small depth of field, while a small aperture (a large F/number) will produce a wider depth of field. This tends to be the easiest variable to control, as your ability to alter focal length and subject distance may be limited. If you want to isolate your subject with a narrow depth of field, set your aperture to f/2.8 or f/4. On the other hand, if you want everything in your frame to be in focus, an aperture of f/16 or f/22 would be appropriate.
If you can vary your focal length or the distance between you and the subject, you can further fine tune your depth of field. Longer focal lengths such as 300mm will give you a more narrow depth of field. This is why macro lenses tend to have longer focal lengths, especially if they are designed for shooting insects. On the other hand, shorter focal lengths like 30mm will produce a broader depth of field. This is why the best landscape lenses tend to be wide-angle lenses. Additionally, moving closer to your subject will also narrow the depth of field.
Using depth of field
While you can calculate your exact depth of field with complex mathematics, the easiest way to achieve your desired depth of field is simply to experiment. Remember that when looking through your viewfinder, you are viewing your subject with the lens aperture wide open, so you will not be able to predict how the depth of field will look in the final photograph. Many cameras are equipped with a depth of field preview button which will close the aperture down to your selected setting and allow you to view the frame before snapping the shutter. In most cases, it is difficult to tell what is and what is not in focus, especially since narrowing the aperture also limits the amount of light coming through the lens. Owners of digital cameras may find it easier to bypass this trick used by film camera users and rely instead on their digital screen to view the outcome. Make sure to zoom in on your final product before finishing your shooting, as the tiny screens on the back of cameras will make it look like more of the frame is in focus than it really is.
Tags: depth field, narrow depth, narrow depth field, depth field, depth field This, field This
