| The way a subject is reproduced in a photograph | | | | it. So if you photograph a distant subject such as |
| can be very different from how it looked to you | | | | a landscape and focus on infinity you waste lots |
| as you took the picture. When you cast your eye | | | | of depth-of-field. By focusing a little closer, you'll |
| over a scene, everything in it seems more or less | | | | extend the depth-of-field at the front so it comes |
| equally sharp, but sometimes in the finished shot | | | | nearer to the camera, while still making sure that |
| only part of the subject appears acceptably sharp. | | | | infinity falls within the depth-of-field behind the |
| This zone of sharpness is called the depth-of-field, | | | | actual point of focus. |
| and it extends in front of and behind the point | | | | You can guess the hyperfocal focusing |
| that you actually focused on. The size of the | | | | distance, but life is much easier if your lens is |
| zone is determined by three key factors - the | | | | marked with a depth-of-field scale. This used to |
| aperture of the lens, the focal length of the lens | | | | be regarded as an essential feature, but with the |
| used, and the distance you are from the subject. | | | | development of wide-ranging zooms many |
| Varying these three elements allows you almost | | | | manufacturers now omit one. If you do have |
| complete control over the depth-of-field in a | | | | such a scale, simply line up the infinity mark |
| picture. | | | | against the mark for the aperture you've set and, |
| When most of the picture is sharp, we say | | | | although the image in the viewfinder will look |
| there's lots of depth-of-field. When only part is | | | | out-of-focus, the finished image will be sharp from |
| sharp, we say depth-of-field is limited. As we'll see | | | | front to back. |
| later, whether you go for extensive or limited | | | | |
| depth-of-field depends upon the subject matter | | | | 2 Main subject sharp with background completely |
| and how you want to depict it | | | | out-of-focus. |
| Three main factors that can be used to control | | | | There are some subjects where you want the |
| depth-of-field | | | | main subject to stand out strongly from an |
| 1 The aperture. | | | | out-of-focus background. Portraiture, where the |
| There's a simple, direct relationship between | | | | emphasis is on the person, rather than the |
| aperture and depth-of-field - the smaller the | | | | location, is probably the most popular area. What |
| aperture, the more extensive the depth-of-field. | | | | you need here is a use a telephoto lens at its |
| So if you want to keep as much as possible | | | | widest aperture. It's also worth moving the |
| sharp, you should set as small an aperture as | | | | subject as far away as possible from the |
| possible - preferably f/16, or even f/22 if your | | | | background - in cramped studio situations this is |
| lens offers it. | | | | often impossible but outside against a wall or |
| Depending on lighting conditions and your film | | | | foliage it's usually easier. Take care, though, that |
| stock, you may need to use a tripod or some | | | | you focus accurately, as the limited depth-of-field |
| other form of support at such small apertures, as | | | | will be unforgiving of any focusing errors. For |
| the resulting long shutter speeds create a risk of | | | | portraits focus on the eye for the best results. |
| camera-shake. | | | | |
| If, however, you want to concentrate attention | | | | 3 Main subject sharp, with background |
| on just one part of the scene, and throw the rest | | | | out-of-focus but still recognisable.Sometimes |
| out-of-focus, you should select a large aperture. | | | | throwing the background completely out-of-focus |
| Exactly how large this can be depends on the | | | | is going too far. You want to show the subject in |
| maximum aperture of the lens you're using. On a | | | | its natural environment, but with the background |
| 50mm standard lens it will be f/1.7, f/1.8 or f/2, | | | | toned down to it doesn't compete for attention. A |
| but on a standard zoom it will typically be f/3.5 or | | | | person on the beach, for instance, an animal in the |
| f/4.5. | | | | zoo, or a flower in a garden. Here a standard to |
| For general picture-taking, when you want most | | | | short telephoto lens, somewhere from 50mm to |
| of the picture to be in focus, you might want to | | | | 135mm, is ideal - especially if it's coupled with a |
| set a middling aperture of around f/8 to f/11. | | | | middle range aperture of around f/8. |
| This is what a program exposure mode sets | | | | |
| when left to its own devices Whenever possible | | | | 4 Zone of sharpness deliberately |
| you should take control of aperture selection and | | | | limited.Occasionally you may want to limit the |
| use either an aperture-priority or manual mode. | | | | depth-of-field to a very specific zone. Maybe in a |
| Four common techniques using depth-of-fieldUse | | | | portrait you want just the eyes in focus, and not |
| these four common approaches when planning a | | | | even the ears or the tip of the nose. Here, once |
| shot to ensure depth-of-field works for you | | | | again, a depth-of-field scale on the lens helps, or, |
| 1 Everything sharp. | | | | failing that a depth-of-field preview facility on the |
| With subjects such as landscapes, groups, interiors | | | | camera, This will give a visual indication of what |
| and travel you'll usually want to keep everything | | | | will and won't be in focus by manually stopping |
| sharp. Using a wide-angle lens set to a small | | | | down the lens. |
| aperture will give you extensive depth-of-field, | | | | |
| perhaps from around one meter through to | | | | SummaryOverall, the practical use of |
| infinity. But there will be times when foreground | | | | depth-of-field can be summed up as follows: |
| interest is closer than that. Here you need to | | | | To maximise depth-of-field and have as much |
| resort to a neat little technique called hyperfocal | | | | sharp as possible use a wide-angle lens, set a |
| focusing that allows you to increase the | | | | small aperture and stand back from your subject |
| depth-of-field. | | | | To minimise depth-of-field with only a small zone |
| As a rule-of-thumb, there's twice more | | | | of the scene sharp use a telephoto lens, set a |
| depth-of-field behind the subject than in front of | | | | large aperture, and get closer to your subject. |