The Mission
– Gain an understanding of how to control depth of field for creative purposes
Time
– One hour
Skill level
– Beginner
Kit needed
– ‘Fast’ lens
Focal length
The depth of field is governed more by the ‘actual’ rather than the ‘effective’ focal length of a lens. With Nikon cameras, you’ll therefore get a tighter depth of field when shooting with an FX format body, than with a DX format body. This is because the smaller image sensor of a DX camera has a 1.5x crop factor that magnifies the overall effective focal length.
Short focal length
In architectural and landscape shots, when you want to keep everything looking sharp from the near foreground to the horizon, a wide-angle lens with a short focal length will give you a large depth of field – especially when used at a narrow aperture. The crop factor of a DX format outfit helps, as with this shot taken at a focal length of 18mm and an aperture of f/16.
Close range
The depth of field shrinks largely at short focus distances, when shooting close-ups. The back of this matchbox toy bus is 4cm further away from the camera than its front. Shot at close range with a 0.5x or 1:2 macro magnification factor, even a narrow aperture of f/22 can’t give enough depth of field to keep the whole model sharp.
Wide aperture
For portraiture, still life and other styles of shooting where you want a tight depth of field, a longer focal length or zoom setting is preferable, along with a wider aperture. This shot was taken at a focal length of 85mm, with a zoom lens’s widest available aperture of f/4, to isolate the main subject against a blurred background.
Work it out
There’s a variety of apps and websites that you can use to work out the depth of field for combinations of image sensor size, focal length, focus distance and aperture. Some lenses have a focus distance scale complete with depth of field markings for certain apertures.
Prime example
Prime lenses usually have a ‘faster’ aperture rating, meaning that they enable faster shutter speeds at their widest aperture setting. Switching to an 85mm f/1.8 lens for this shot, you’ll notice that the smaller depth of field has enabled more blurring of the background. The visual quality of the background blur in this instance is known as ‘bokeh’.