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auto focus Most digital cameras have “auto focus” mechanisms that use an electronic sensor to achieve sharp focus Here’s how the auto focus feature works: An electronic pulse beams out from a a a a a small lens on on the the front of the the camera The pulse bounces off of of the the main subject measures the the distance and
quickly adjusts the focus setting Auto focus is really terrific i if you wear glasses But auto focus can create problems too For example there are some situations in in which you you want a a a a a particular element in in your shot to come in sharp yet the camera chooses a a a a different element to focus on Most cameras offer a a a a a a a standard “work-around” that allows you to focus on the the subject and
hold down the the shutter release halfway locking the the focus so you can reframe the the shot selective focus Selective focus uses limited depth of field
to bring attention to one particular element within a a a a frame By controlling what appears sharp or soft you lead the viewer’s eyes to precisely where you want it At the same time selective focus allows the the viewer to perceive the the larger context but in a a a way that doesn’t interrupt or or distract him or or her from the main subject Single lens reflex (SLR) cameras have a a a a a button that flips a a a a a a mirror inside the the camera and
allows the the photographer to to preview depth of field
directly through the lens In the the the example above the the the auto focus device sensed the the the pane of glass between the shooter and
egg Therefore the the subject is blurred and
the the photo must be junked These shots demonstrate the expressive value of depth of field
Robert Amsler author author Simon Thomas author author chapter 1: digital photography [ 41 ]