Depth of field in an image refers to the range of distance in an image that shows acceptable sharpness.
We all know the theory – large apertures such as f/2.8 will result in your subject popping out of a lovely, soft background whereas small apertures such as f/22 will result in a a lot more of the image being in focus.
Yes, a large aperture is preferable in wildlife photography as it gives you a huge amount of creative control over the look and feel of your images but shooting wide open all the time can result in missed shots.
Last week we were photographing a massive troop of baboons along the Chobe river. Love shooting theses guys and especially in a large group they make for amazing photographic opportunities as there are little ‘stories’ happening all over the place.
I had my lens pointed at one of the youngsters as he was nibbling on a piece of grass.
With an aperture of f/5 dialed in at a focal length of 600mm my focus was locked on the young primates face. Being quite close to him I chose these settings as the background was potentially very distracting and I wanted to throw it out of focus while getting the head sharp from front to back.
As I shot one of the frames the youngster lifted his hand which my autofocus locked onto and I ended up with this shot.
A perfectly sharp hand with a soft and out of focus face.
According to the depth of field calculator on DOFmaster.com the combination of my chosen aperture, focal length and distance from my subject gave me a depth of field of 18cm. Not a helluva lot. On a side note, the iPhone app from DOFMaster is pretty cool as well!
I was quite happy with a small depth of field and if I locked onto the baboons’s face it would have been perfect – sharp head from front to back – but with the hand popping up and throwing off my focus point the 18cm was not enough to get the face sharp as well.
When the little guy dropped his hand I shot another few frames and this time I locked onto his face with the exact same settings.
This time a depth of field of 18cm was perfect to create a portrait that shows the important part of my subject while at the same time throwing the background and foreground out of focus to keep the visual attention on my subject.
When you’re out in the field make sure you understand the affect of the various factors that influence depth of field. As a reminder, they are:
- Focal length
- Distance to subject
- Distance from subject to background
The difference between a great image and a dud is very small indeed.
Until next time.