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You've probably seen plenty photos taken with wide apertures (we've written about this technique before on Phototuts+). They are easy to recognise because of the shallow depth-of-field. Normally, these photos are taken with a prime lens. But don't think that you have to use a prime lens to get this effect. It certainly helps – but the world of wide aperture photography is open to everybody that owns a digital SLR, regardless of which lenses you have.
Today we're going to dive into the technique, settings, different subjects, and available lenses for this type of photography.
Let's start off with some images showing what you can do when you use your lens's widest aperture setting. The main advantage is that you can take photos with out-of-focus backgrounds. This is a creative technique that focuses the attention on your subject by reducing the background to a blur.
Your eye is attracted to sharp areas in a photo before it goes to unsharp areas. So selective focus becomes a useful tool to emphasise the part of the subject where you want the viewer to look first.
Photos of people often benefit from an out-of-focus background. The important thing is to focus on the eyes. You can create some magical effects by getting in close, focusing on the eyes and using the widest aperture on your lens.
Try this with the longest focal length lens that you have. If you are shooting in colour, look for colourful backgrounds that add atmosphere to the photo when they are out of focus. A good example is red coloured autumn leaves, as in the photo above, shot at f1.8 with an 85mm prime lens.
Flowers also look good with out-of-focus backgrounds. The trick here is to find flowers that are located some distance from whatever is behind them. This ensures that the background will be as out-of-focus as possible.
Green backgrounds are good because they look natural and also enhance the bright colours of the flowers. This photo was taken at f4 with a 17-40mm zoom lens.
Animals are another subject that benefit from an out-of-focus background. This photo of lizard illustrates the point – the background isn't distracting because it is extremely blurred. I focused on the lizard's eye, just as if I was taking a photo of a person. It was taken at f1.8 with an 85mm lens.
Zoos and other places where animals are kept are great places to practice this technique. I found this lizard in a botanical garden, and as it was used to the presence of people, it let me get quite close. You'll need a telephoto lens if you can't get so near.
A good technique for travel photos is to look for details that capture the atmosphere of the place that you're in. This photo of a hand-made horse's stirrup is a good example. It was taken in Argentina, on a horse belonging to a Gaucho, one of the icons of Argentine culture.
By using a wide aperture, the background is thrown out-of-focus and the viewer's attention is directed to the stirrup. Taken at f4 with a 50-150mm zoom lens.
You can also use wide apertures to create abstract images by focusing on a single point within the image and throwing the rest out of focus. If you are observant you can make suprisingly good images from everyday items – such as this photo above. The metal spirals were part of a chair that I was sitting on outside a cafe. Taken at f3.5 with a 50-150mm zoom lens.
There is an overlap with travel photography here, but the wide apertures of telephoto lenses are ideal for blurring potentially distracting backgrounds. A background that is out-of-focus, but still recognisable, can be very evocative.
This is a technique used in movies to create mood. I did the same with this photo taken in Potosi, Bolivia. I used an aperture of f2.8 and a 50-150mm zoom lens.
One of the key differences between prime lenses and zoom lenses is the maximum wide aperture. Most prime lenses have a maximum aperture of anywhere between f1.4 and f2. There are a few lenses that have wider apertures of f1.0 and f1.2 (and at least two lenses that have an incredibly wide aperture of f0.95).
There are prime lenses with smaller maximum apertures too – they are generally telephoto lenses. But most primes have a maximum aperture of somewhere between f1.4 and f2 – perfect for taking photos with out-of-focus backgrounds.
Another advantage of prime lenses is that you have several aperture settings to choose from at the wide end of the range. If the maximum aperture of your lens is f1.8, for example, you can also use f2, f2.8 and f4. F1.8 may limit the depth-of-field by too much – the other settings give you more creative options.
Zoom lenses have wide maximum apertures anywhere from f2.8 to f5.6. Again, it depends on the model. Lenses aimed at professionals tend to have the widest apertures (they are more expensive too). But it doesn't matter what the widest aperture of your lens is, you can still use it to creative effect. It's just a matter of understanding how depth-of-field works and how to utilise it to your advantage.
The depth-of-field in a photo depends on four things:
The longer the focal length, the less apparent depth-of-field. I say apparent because if you took a photo of the same subject using the same aperture with both a wide-angle and telephoto lens, and the subject was the same size in the frame in both images, the depth-of-field would be more or less the same in both photos.
In practice though, telephoto lenses appear to give you less depth-of-field because they allow you to magnify the subject. Therefore, if you are using a zoom lens, you should set it to the longest focal length in the zoom range.
Worth repeating – the wider the aperture, the less depth-of-field. Set your lens to its widest aperture to minimise depth-of-field. The three photos above show the difference changing the aperture makes.
This is a major factor. The closer you get to your subject, the less depth-of-field you get at any given focal length and aperture. Get close enough and you will won't be able to get front-to-back sharpness even at f16 or f22, let alone at apertures like f4 or f5.6.
This means that close-up photography is a good area to explore if you want photos with minimal depth-of-field, but don't have a prime lens.
Subject to Background Distance
This is another major factor. The greater the distance between your subject and the background, the more out-of-focus the background will be at any given aperture, focal length and subject distance.
This photo of a flower has an extremely blurred background partly because it was taken at an aperture of f1.8, but mostly because the background was far from the flower.
Putting It Together
To make the most of the shallow depth-of-field effect you need to use the longest focal length possible, the widest aperture that your lens has, get as close to your subject as you can, and get as much distance as possible between your subject and the background.
The subject distance is limited by the minimum focusing distance on your lens (this is indicated on the lens barrel – as in the photo above, showing the minimum focusing distance on a Canon EF 85mm f1.8 lens). This is the closest distance you can get to your subject and keep it in focus. But there is an easy way of overcoming this, so you can get closer to your subject and get even less depth-of-field in your photos.
The accessory you need is called a close-up lens (it is also sometimes called a close-up filter or supplementary lens). That's because it looks like a filter and you use it the same way. It screws into the filter thread on the front of your lens and reduces the minimum focusing distance so that you can get closer to the subject.
There are two types of close-up lens. Single-element close-up lenses can be quite cheap but do suffer from chromatic aberrations. You also lose image quality, especially at the edges. But they are a good way of trying close-up photography without spending much money.
Double-element close-up lenses are more expensive but the image quality is excellent. There is little or no chromatic aberration and the edge-to-edge sharpness is good. Double-element close-up lenses have two optical elements, one which corrects the aberrations caused by the first. They are more expensive but worth the extra money if image quality is a priority. The close-up lens in the photo above is a Canon 500D (not to be confused with the Canon camera of the same name) double element close-up lens.
Disadvantages of Wide Apertures
We've already spoken about the creative use of wide apertures to make images with shallow depth-of-field. But there is a disadvantage of using wide apertures that you should be aware of. Lens quality is always poorest at the lens's widest aperture. You will notice increased optical aberrations such as chromatic aberration, vignetting and a lack of sharpness at the edges of the image. More expensive lenses have less aberrations.
There's not a lot you can do about this except to be aware of it. One step you can take is to shoot using the RAW format. This is because most RAW converters can now correct chromatic aberrations and vignetting. However, they can't do anything about the fall-off in image quality at the edges of the photo.
Using wide apertures is a great way of taking some unusual, moody photos. Here are some links to the Flickrstreams of three photographers that use wide apertures to great effect in their work. Their photos will inspire you and give you some ideas of how to use this technique in your own work. Admittedly, they are using prime lenses, but don't let this put you off using the widest aperture on your zoom lens if you don't own a prime lens.
A photographer that uses wide apertures brilliantly. One of his lenses is a Noctilux 50mm f1.0, which he uses on a Leica M6. There are lots of good portraits on his Flickrstream.