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Depth of Field

roy frankland tyne valley express depth of field image

(how to make your subject really stand out!)

If you cast your minds back a few editions, we discussed exposure, and the various things you have at your disposal to get your exposure correct. We talked about the balance between ISO setting, shutter speed and aperture and very briefly, I went through each of those and the effect they have on your image. Well, I’ve recently been on holiday in South Africa which included a safari visit for some wildlife and bird photography. This got me thinking about a subject for this article, as control of depth of field is very useful when it comes to photographing wildlife and birds as well as portraiture. So, what we will look at this time in more detail is how to control your depth of field to really help your subject stand out. Depth of field is defined as the distance between the closest and farthest objects in a photo that appears acceptably sharp. Your camera can only focus sharply at one point, but the transition from sharp to un-sharp is gradual, and the term ‘acceptably sharp’ is subjective!

When you are shooting subjects such as birds or portraits, and sometimes wildlife too, you want the subject to really stand out separately from the background and a good way to do this is to make the background blurred and out of focus, while keeping your subject nice and sharp, in other words, a shallow depth of field. This is achieved through control of your aperture, (the hole through which light enters your camera). The aperture is the size of the opening in your lens and is expressed as an ‘f’-number or f-stop, e.g. f2.8, f8, f11 etc. The smaller this number, the bigger the aperture (hole) and the bigger the number, the smaller the aperture. So f2.8 will be a wide opening whereas f22 would be very small. The maximum/minimum will depend on your lens capability and specification. The smaller the f-number, the less depth of field and the bigger the f-number, the greater your depth of field.

So, to get back to our bird or portrait images, what we want to do is make your subject sharp and well defined, while taking away any distractions in the background by blurring it out. You can see examples of this in the accompanying images. In some wildlife shots, you may want to include the environment of the animal which would then require a wide depth of field, but for the purposes of this article, let’s assume you want to focus in of the animal itself, as you would with birds or portraits. When focussing, always try to focus on the eyes!

Firstly, ensure you have a lens suitable for what you want to shoot. For wildlife and birds, (which are likely to be far from you), for example, I use a Sigma 150mm – 600mm f5-6.3 lens on my SLR, although there are many other suitable lenses available. Then you need to select the lowest aperture (f-number) that you can on your lens. This will give you a shallow depth of field and reduce the depth of sharpness in your shot. Another important factor to consider, that affects depth of field, is the distance between the camera and the subject, although admittedly it’s sometimes hard to control. The shorter the distance of your camera to the subject, the smaller the depth of field, so try to get as close as you can.

Remember too that for a good exposure, aperture will need to be balanced with shutter speed and lighting conditions, so If depth of field is most important to you, then you could select aperture priority on your camera and select the lowest option and it will select the best shutter speed for your chosen aperture. When I’m shooting birds and wildlife, I usually keep a high ISO setting of around ISO1600 to make sure of a fast shutter speed to reduce hand shake as I like to shoot handheld as much as possible. Experiment with your camera, find what works for you, and finally, whatever you do, remember to enjoy it!

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