So we all know that depth of field is linked to aperture and that we can use depth of field to control the acceptable range of sharpness/focus in an image. But are you fully aware of how the distance of the subject from the camera affects depth of field?
The image below for example was take with a 300mm F.28 lens at F2.8. Can you see how shallow the depth of field or acceptable range of sharpness is in this instance?
Compare the elephant skin to the image below, taken with the same lens at the same focal length and aperture.
Notice how with the same focal length and aperture I have two incredibly different resultant depths of field. On the first only a very small portion of the skin is sharp and in focus, yet in the second, I have the full length of the rhino sharp and in focus. The only variable that has changed and has impacted on the depth of field is simply the distance of the subject from the camera.
With the help of this Online Depth of Field Calculator I am able to show you exactly how the change in distance has affected the depth of field in these two situations. Take note of the total depth of field that we are able to achieve at f2.8 at the two distances.
Image 1. Elephant Skin at 300mm, F2.8 @ 2.25m from the subject
Image 2. White Rhino at 300mm, F2.8 @ 80m from the subject
Things to Remember
The next time you are out in the field remember that your resultant depth of field is not only determined by your aperture setting, but also by the proximity of your camera to the subject. The closer you are to the subject, the shallower the resultant depth of field will be at a constant aperture and focal length.
In laymen’s terms, if you are photographing a leopard approaching your vehicle with a 300mm lens set to f 2.8, you need to be aware that the closer it gets to you, the shallower your depth of field will be. You will therefore need to compensate for this by adjusting your aperture to a larger F number (resulting in a smaller aperture) in order to keep more than just the tip of the nose sharp.
This was one of the many take home points we discussed during this weekend’s Wildlife Photography Course.
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