Dof at 70mm Dof at 300mm

Depth of field

Depth of field refers to the distance between objects in a photo that appear to be in focus. This is affected not only by the f stop, with a smaller aperture giving a greater depth of field, but also the focal length of the lens being used. In the photo to the left which was taken with a 24-70mm f 2.8 lens set at f 4 with a 70mm focal length you can see a greater range of graduations that are in focus, as compared to the photo on the right, which was taken with a 300mm lens with an aperture of f 4.