What determines depth of field? There are three factors that contribute to the depth of field
that is available to you for any picture you plan to take. Let??™s look at these factors one at a time
and then combine them.
?– Aperture The aperture of your lens is the first major factor that influences depth of
field. We talked about aperture back in Chapter 3??”it??™s the size of the lens opening that
determines how much light reaches your camera??™s imaging sensor. Aperture is measured
in f/stops, where lower f/numbers represent bigger openings and higher f/numbers
FIGURE 4-11 Successful pictures are often a matter of surprising the viewer.
CHAPTER 4: Composition Essentials 85
represent smaller openings. In addition, the smaller the aperture??™s actual opening
(in other words, the higher the f/number), the greater the depth of field will be. As you
can see here, the aperture of your lens directly influences how deep the depth of field is
in any given picture:
?– Focal length As we will discuss in the upcoming section ???Get the Most Out of Your
Zoom Lens,??? focal length is just a measure of your lens??™s ability to magnify a scene. And
while most people focus on a lens??™s magnification, depth of field plays an important role
here as well.
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