DEPTH OF FIELD

by Kenji




Do you sometimes wonder how some portrait shots are taken with the lovely blurred background or how an amazing landscape shot remains beautifully sharp right from the grass in the foreground up to the tip of the mountains in the horizon? This is where a little technical knowledge about depth of field will help you to create remarkable shots like these as how professional photographers do it.



What is Depth of Field?


Depth of field refers to the zone of accepted
sharpness starting from in front to the back of
the focused plane. Here it is shown as the area
between the green lines. In reality, the sharpest
point of this image is a single plane or line, shown
in red. Anything before or beyond the line is a
gradual drop in focus.



Depth of field is affected by aperture size, focusing distance, focal length of the lens and the size of the camera’s sensor or film. A larger aperture results in a shallow DOF whereas a smaller aperture would result in a deeper DOF. In the case of focusing distance.

Depth of field is also affected by the size of a camera’s sensor. To put it in a simple context, smaller digital cameras is unable to create depth of field as shallow as DLSR’s because the sensors on these cameras are small. In some ways, this is a good thing as snapshots taken with a small digital cameras can result in mostly sharp details because of the deeper depth of field.




Flowers make great subjects to isolate
using DOF as they are relatively small,
therefore requiring one to shoot up-close
for a shallow DOF



DLSR’s and prosumer cameras have manual functions on them, leaving you to
be in full control. In situations where your focus is the subject, a shallow depth of field using a large aperture (eg f/2.8 to f/5.6) and a long focal length is best used to isolate your subject from distracting background elements.

If you are taking a picture of your subject against a beautiful background and would like to have both clearly visible, use a short focal length or a wide-angle lens coupled with a small aperture (eg f/16 to f/22) to get a deeper depth of field. Remember to focus on your subject before recomposing with the background. Good lighting is also a key consideration here as a small aperture will require a slower shutter speed.




A very shallow depth of field has isolated
this flower from the background making it
look almost 3 dimensional in a 2 dimensional
form




This picture was at f/5.6 using a
telephoto lens to effectively blur the
background and isolate the subject




This picture was taken at the same setting
but using f/16 for a deeper depth of field,
to produce an acceptably sharp foreground
leading into the background



Usually for most photography situations such as shooting family, friends, buildings, and even large landscape area, many photographers leave it to the camera for the best aperture and shutter setting. This would be almost always be on medium setting rendering everything at more or less sharp.

For fully automatic cameras, the program settings (ie, portraiture, landscape, outdoors and etc,) have been preset so that the cameras adjust the aperture and shutter speed to the required effect. This is particularly useful for digital cameras with no manual settings, thus allowing for some basic creative photography effects.




When taking portraits where the emphasis
is on the subject, a shallow DOF helps to
bring to focus towards the model. This
picture was taken at f/2.8 with a 180mm
focal length setting



In macro photography, where your subject is almost or as small as your camera’s sensor, depth of field is restricted to the shallow end. Any tweaking would only result in a limited range of depth. Therefore, getting your point of focus right is crucial for a good picture. A simple subject can be made to look strongly 3-dimensional by being the only sharp element in the frame.







When you are shooting architecture with large shapes and form, remember to set your camera for a deeper depth of field as you would want to get the entire structure as sharp as you can get it to be. This is the same when you shoot a large landscape expanse. Professional photographers know to use a good wide angle lens and shoot from a low viewing angle in order to get foreground elements in the picture to lead viewers into the picture. This method requires one to set the camera for a deep depth of field.




With a scene like this, a very deep depth
of field is essential. Notice how the chinese
characters stay readable even in the distance




Here is another picture where proper consideration
of foregrouund and background details were taken
into account. This shot was taken at f/22 with a
28mm wide-angle focal length.