16 July 2011

Depth of Field

15 July 2011

The depth of field is the amount of your image beyond and before your focal point that will be in focus.  Normally, for landscape, you want a large depth of field and to have everything in focus to capture the beauty of the scene.  In portrait photography, a small depth of field is often used to limit distractions of the background  from the main subject.

There are a few factors to determine your depth of field:

1)  Your aperture
2)  Your lens
3)  the distance from your subject.

The Aperture
The aperture controls the depth of field, which is what is in focus in your image.  You can draw attention to one subject, with a blurry background using a low f/stop or to focus everything in an image with wide f/stop. 

This is f/5.6 with a close distance

  Here I widened the apurture to 7.1 and stepped away a few feet. Notice how the baby's hand is not in focus, this is because my focal point was broader than the movement of the hand.

•    The higher the number for your f/stop the wider your depth of field (f/16) the lower the number for your f/stop the more shallow is your depth of field. (f/8)
•    The closer to your image, the shallower is your depth of field as in using a micro lens for nature photography. 

Here are some other shots, showing the depth of field using higher/lower f-stops.
This image was taken at f/16 a smaller aperture. Notice how you can see more details of the dark Cyprus trees in the background compared to the image below taken at f/13.  This image has a "broad depth of field"

Taken at f/13 you can still see the background, but the trees and wall are not as "sharp" in focus as the f/16 shot.  I call this a "medium depth of field".
This image was taken at f/8 you notice how the garden in the front is the main focus, while the background is blurred.  This image has a "shallow" depth of field"

Your lens:

•    The longer your lens (200mm) the more shallow will be your depth of field.   The shorter your lens (55mm) you will have more depth of field.  This is termed as Focal Length.

The Distance:

•    The closer you are to your subject, the less amount of depth of field you will have.  The farther away, the more depth of field.  (as described in the image of the baby's hand and other image with the mother above)
Related lessons:
Aperture and f/16 Rule
Shutter Speed Basics

Depth of Field
Focused Bracketing or Photo Stacking 

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