4. Camera Focus
Understanding focus is key to taking good photographs. You may be thinking, the camera does it all for you, doesn’t it? With modern DSLR cameras, that’s often the case, but knowing how to focus manually will help you achieve much more creative results.
When you take a photo, light passes through the lens on your camera before it reaches the recording medium. The lens, regardless of whether it’s built into your camera or interchangeable, contains various elements that focus the light.
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Manual focus vs autofocus
Most modern lenses can be focused both manually (MF) and automatically (AF). You can adjust this setting on the lens itself.
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You can set the focus manually by adjusting the focus ring of your lens. Manual focus is useful when your camera has difficulty focusing, or when you’re taking a series of images in which you don’t want the focus to change.
Autofocus refers to the mechanism that automatically moves the elements within the lens in order to achieve the best focus. This is done through a series of autofocus points that are visible through the viewfinder. The camera (or photographer) selects a particular focus point and this is used to achieve focus.
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Above are two examples of what you can expect to see through your viewfinder. This not only shows how different cameras have different focus layouts, but also how they have a different number of focus points for you to choose from.
Your camera automatically selects a focus point in one of two ways:
Phase detection: This is the system most commonly found in DSLR cameras. Phase detection is very fast, which makes it great for tracking moving objects. Although the system doesn’t always get it right, this technology continues to improve.
Contrast detection: This system is commonly used in mirrorless cameras, point-and-shoot cameras, DSLRs in live view mode and smartphone cameras. Much simpler than phase detection, it is slower but much more accurate, which makes it far better suited to genres like product or landscape photography.
Different cameras have different focus systems, and different focus points. Depending on the focus mode you choose, you or the camera can choose the best point of focus. Some modern cameras also feature eye detection, which can be very useful as they eyes are often the best place to focus.
Focus modes
When you’re using autofocus, there are a number of different modes to choose from. Each is best suited to particular scenarios.
Single shot/Single-servo focus mode: Only one focus point is used to determine focus. This does not change until you refocus. This is shown as ‘One-Shot’ on Canon / ‘AF-S’ on Nikon.
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Continuous focusing/Continuous-servo: Once a focus point is set, the camera monitors the distance of the subject from the camera and readjusts as necessary for as long as the focus button is held down. This is shown as ‘Al servo’ on Canon / ‘AF-C’ on Nikon.
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Automatic autofocus mode: This is a cross between single shot and continuous focusing. The camera focuses on a single subject and only refocuses when the subject moves. Until that point, the mode behaves more like single shot than continuous focus.
Where to focus when taking a photo
Where you focus in an image depends on a number of factors, most notably what you’re photographing and what result you want to achieve. In the video above, you can see how different focus points can have a big impact on an image.
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When selecting your focus, it’s important to think about two specific things: your subject and depth of field. What do you want to be in focus, and how much of the subject do you want to be sharp?
Depth of field (controlled by adjusting the aperture) will increase or decrease the sharpness either side of your focus point. We’ll look at this in more detail in the next chapter.
WATCH NEXT: Class 5: Aperture and Depth of Field
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