A Guest Post by Wildlife Photographer Elliot Hook

Depth of field is often discussed when reading about wildlife photography, usually with the emphasis on ensuring that a small enough depth of field is used to guarantee that the background is thrown out of focus to give emphasis to the subject. However, it is important to ensure that the depth of field you obtain is still large enough to render the entire subject in sharp focus – what good is an image that has a beautifully soft, distraction free background, if the subject itself is not in focus.

A red kite taken at a falconry centre, at 150 mm, f/5.6, from approx. 1m. Notice the softness of the tip of the beak and feathers on the top of its head, even though the eyes are pin sharp.

Depth of field is controlled by a number of factors (aperture, focal length and distance to the subject) and to a beginner reading about wildlife photography, the overarching message will often be ‘the larger the aperture the better’ to achieve the classic wildlife shot with the soft background. Without an understanding of the depth of field that your camera and lens combination will achieve in a given situation, it may mean that you come back from a day of photography with a set of images that are disappointing when viewed on a large screen.

I am writing this from personal experience. My appreciation of aperture used to be limited to knowing that I needed to select the largest aperture possible to ensure I achieve the ‘most out-of-focus’ background. Also, increasing the aperture would often be my first port of call to remedy slower shutter speeds (as opposed to considering the ISO level) meaning that I would often find myself shooting at f/5.6 on my 300 mm zoom lens (not even considering the sharpness performance of the lens when used wide open – a subject for a whole other article).

Last year, I spent the day at Donna Nook, in Lincolnshire, UK, photographing grey seals. Little did I realise that when using an Olympus DSLR (2x crop factor due to the small sensor size), a focal length of 300 mm, and an aperture of f/5.6 to photograph a seal that was approximately 5 metres away, the resulting depth of field would be less than 5 cm. Considering the size of a grey seal, even if I managed to get my focal point spot on the eyes, there was no chance that the tip of the nose would be in focus, let alone the rest of the seal’s head. After what I thought was a fantastic day shooting, taking in excess of 500 photos, the number of images that I was actually happy with was fewer than 5!

It was after this experience that I found online depth of field calculators (apps also available for android and iOS users) that would calculate the depth of field for your camera, given a set of basic parameters – camera type, focal length, aperture and distance to the subject. Often used to calculate hyper-focal distances for landscape photography, the calculators can be incredibly useful for shooting wildlife too – it became evident to me that depending on how close the subject is, I could end up with a depth of field of less than 1 cm!

The blue tit, taken at 300 mm, f/10, from approx. 3 m. Bird and perch sharp throughout, with a diffuse background.

To put my new found knowledge to the test, I started trying to take photographs of blue tits in my back garden. I had set up a perch at a distance of approximately 3 m from where I was sat. Using a focal length of 300 mm, I found that I needed an aperture of around f/10 to ensure a depth of field of approximately 4 cm. After some waiting, I managed to capture the shot I had been waiting for, a perfectly sharp blue tit, on a perch with a beautifully soft background, all using an aperture of f/10 – smaller than most tutorials for wildlife photography recommend.

This has fundamentally changed the way I think about my camera settings. I no longer plump for f/5.6 but always think about the magnitude of the depth of field I want to achieve for any given subject and adjust my aperture accordingly, with the confidence that I will still get the soft background I am after, but with a pin sharp subject that gives the resulting image even more impact.

Elliot Hook is an amateur wildlife and landscape photographer who never stops learning. He can be found at www.elliothook.co.uk

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