Chapter 3. Focus and Depth of Field
Focus is perhaps the most important component in the success of an image. We all focus our eyes in the natural process of seeing, although lighting conditions, attention span, and our emotional engagement with the scene impact exactly what we comprehend and react to. Thus, we use our eyes to bring the world into optical focus, but we also focus our minds to concentrate our attention on the things we're trying to understand.
This chapter looks at the act of focusing with both our eyes and our minds. Getting the camera to render the world in sharp detail is the first step, while controlling what is in or out of focus allows us to create emphasis and to control the composition of the image. This chapter starts by outlining the basics of digital focusing techniques, and moves quickly to explaining how to control depth of field effects.
The final pages of this chapter present tips for controlling focus and depth of field in specific types of scenes, including landscapes, objects, and close-up photography.
Focus, Sharpness, and Depth of Field
Focus and sharpness may sound like the same thing, but they really are two related but separate components of good photography. Sharpness refers to the crisp clarity and detail present in a photograph, while focus refers to the controls and action required by your camera to achieve the final sharpness result.
Camera manufacturers have been on a holy quest to get us to forget about focus, assuring us that the cameras are automatic and intuitive enough to read the sceneas well as our minds. Although this is often true, there are times when the camera is less than intuitive, and we have to give it a nudge to get the focus right. To help you do that, we're going to examine the mechanics behind focusing systems, explaining how they work and when you should shift from auto to manual.
Focus is also one of the means by which you determine a photo's depth of field. Depth of field is interesting because it controls what parts of the image are in focus as well as the overall clarity of the subject. Thus depth of field plays a significant role as a compositional element, controlling where the viewer looks and the speed with which his or her eyes move through the scene. These issues are covered in greater detail in the next chapter on composition, but for now, the important thing is to understand what depth of field is and how to control it.