06 Apr 2010

The Author

Andy Lim got started in photography after leaving design college, and has given several public talks on the subject of photography. SimpleSLR Workshops Photography workshops from beginners to advanced levels. SimpleSLR Guides Author of best-selling e-book series. Photography Tips Author of useful and practical tips on GoodPhotography.info website. Emotion in Pictures Accomplished professional wedding photographer. His brand attracts clients worldwide with his unique flavor of wedding and portrait photography.

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Using Depth of Field

Depth of field is sometimes incorrectly used to refer to the “out-of-focus-background” look that’s very popular when shooting portraits. That is half-correct because it refers only to shallow depth of field. Sometimes it’s also confused with bokeh, which is essentially the quality of the out-of-focus portions of an image.

Going to the other extreme and getting the flowers, huts and mountains (and people too) sharply focused in a landscape photo requires deep depth of field. That means a sharp foreground and background as well.

Depth-of-field is the area that is sharply focused, which is controlled by 3 factors:

  • Aperture (larger apertures like f2.8 give you less depth-of-field, smaller apertures like f16 give you more)
  • Focal length (telephoto lenses have less depth-of-field, while wide-angle lenses have more)
  • Distance between subject and camera (the closer you get, the less depth-of-field you’ll have)

The most common factor of depth-of-field is the aperture setting. The aperture is usually taught in basic photography classes as the main factor that affects how much depth of field there is in your photo.

A big aperture (which means a small F number like F1.4 or F2.8) will give you shallow depth of field, while a small aperture (which means a big F number like F11 or F16) will give you a deep depth of field.

This works well on SLR and DSLR cameras, but on point-and-shoot compact digital cameras, the differences are difficult to spot. This is because point-and-shoot compact digicams have very small sensors and inherently come with deep depth of field, even at an F2.8 aperture setting which is common in point-and-shoot cameras. That means it’s pretty hard to get the shallow depth of field effect on point-and-shoot cameras, unless it has a longer zoom range (like 10x), which brings us to the next factor in controlling depth of field.

Your lens focal length is the next factor. Longer lenses (telephoto lenses) like a 200mm lens will give you shallow depth of field, while wide angle lenses like a 10mm lens will give you plenty of depth of field.

Aperture: f2
Focal length and
distance is constant
Aperture: f8
Focal length and
distance is constant
Aperture: f22
Focal length and
distance is constant
Low depth-of-field
(background and foreground
is blurred)
Medium depth-of-field
(background and foreground
sharpness is average)
High depth-of-field
(background and foreground
is sharp)
DOFman med Using Depth of Field
DOFman high Using Depth of Field
Area of focus is small Area of focus is average Area of focus is large

DOFaperture large Using Depth of Field



DOFaperture med Using Depth of Field



DOFaperture small Using Depth of Field


f2 is a large aperture f8 is a medium aperture f22 is a small aperture
 

The range of apertures differ from one lens to another.

The third factor is distance to subject. Did you know that if you moved in closer to your subject, your depth of field will also be decreased, ie. a shallow depth of field? This works well if you’re using a point-and-shoot, and are trying to get that “out-of-focus-background” look. That is also why when we shoot an object really close (as in macro photography) we tend to naturally have shallow depth of field, forcing us to use a smaller aperture to get an acceptably sharp picture of a really small object.

16 Using Depth of Field

This photo above was taken with an F2.8 aperture setting, and focused very close, with a wide angle lens.

23 Using Depth of Field

The photo above used a wide angle lens with a small aperture (F11), which leads to a slower shutter speed.


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