When taking a photo, most people only think of ‘Focus’ in terms of focusing on the subject, and taking the shot. And thats fine. You’ll get a decent shot, where your subject is in sharp focus, and a lot of the time, pretty much everything else in your shot will be in focus too. But having a background and foreground that is OUT OF FOCUS, can make an outstanding difference to your final image, because it literally focusses all the viewers attention on your subject, and turns everything else into a soft, creamy, beautiful blur.
This is very effective in portrait shots, and works extremely well on close ups – objects, jewellery, food shots, flowers, products etc.
There are two ways to achieve this effect – Aperture setting, and choice of Lens.
With Aperture setting, to achieve that dreamy out of focus background, you need to get your aperture (iris) wide open. When your camera is on AUTO settings, and sets the aperture for you, it tends go to the mid range of aperture settings, around F5.6, giving you an image where most, or all of your image is in focus. But if you open it right up to F2.8 or F2 (or even lower if your lens is able to open up further) then this gives you a shallow ‘depth of field’. Depth of field refers to how deep the focus is, from the focus point on your subject in relation to everything in front and behind it. So with a low depth of field, the spot you focus your lens on will be in focus, but everything in front and behind it, will be out of focus. With a high depth of field, say F11 or F16, the focus is much deeper, and will go all the way form the foreground to the background, so everything in your image is sharp.
So your aperture setting has a direct effect on the depth of focus in every image you take. And whilst for some images, its fine to have pretty much everything in focus, for other shots, you can create an image with far great impact and beauty, if you open up your aperture to create the shallowest depth of focus you can, so that whilst your subject is pin sharp, everything else is beautifully blurred. This effect is also known as ‘bokeh’.
Another way to achieve this effect is to use a long lens, or the long end (fully zoomed in) of your zoom lens. This also gives you a shallow depth of focus, so if you aren’t sure how to set your aperture manually, then this is another way to try it.
It works best when there is distance between your subject and your background, because the further away things are from your focus point, the more out of focus they will appear. So if you’re taking a portrait shot of someone leaning against a wall or a tree, the wall / tree will only be slightly out of focus, as it’s still relatively close to the focus point. But if your subject is standing in say, a garden, and the background is several meters behind them, the background will appear very out of focus.
Its worth pointing out that when taking a portrait shot, the point of focus should always be the eyes. This is where the viewer is drawn when they look at a portrait, so the eyes (or if very close, then one of the eyes) should always be what you focus your lens on.
Different lenses have different affects on Depth of Field. The wider a lens is, the wider the depth of field is, and the ‘longer’ the lens is (the more close up it is) the shallower the depth of field is. So by combining the two, you get an even stronger effect. This is one of the reasons why professional portrait photographers tend to use a longer lens – as well as being more flattering, it has a shallow depth of focus, which is often desirable in portrait photography.
Now that you know how to achieve shallow depth of focus, try it out on portraits and close ups, and you will achieve far more beautiful, striking images. When you understand how aperture works, and how depth of field affects your photographs, you make a huge step forward with your photographic skills, and in no time, knowing how to get exactly the image you want, and adjusting your aperture setting, will be like second nature.