Image Sharpness
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Another important principle for taking a great picture is image sharpness.
Image sharpness is affected by several things, including camera shake, depth-of-field, digital noise and lens focus.
Image sharpness can be obtained through optimal focus. AF-Area modes determine how a focus point is selected when in autofocus mode. To select the AF-area mode, hold the AF mode button and rotate the main command dial through the menu. Depending on the model, most cameras have 11 focusing points.
Cameras typically have 3 focus modes: single servo AF, continuous servo AF, and quto-focus. The AF or auto-focus modes focus the images automatically when the shutter is pressed halfway down. The auto focus modes can also be selected by holding the AF button and rotating the main command dial.
Single servo AF is best suited for photographing subjects that are not moving. When focus is achieved the AF point which achieved focus will flash in red, and the focus confirmation light in the viewfinder will also light.
The continuous servo AF mode is best for shooting moving subjects. This mode is for moving subjects when the focusing distance keeps changing. While you hold down the shutter button halfway, the subject will be focused continuously.
Choose single-servo AF for landscapes and other stationary subjects. Continuous-servo AF may be a better choice with erratically moving subjects. Manual focus is recommended when the camera is unable to focus using auto focus.
The last of the focusing modes is the Manual focus or MF mode. Moving the focus switch on the lens to M – manual focus mode - gives you the control to manually focus on any subject through the viewfinder by using the focus ring on the lens.
If you are mastering the focus modes and still seeing poor focus, it may be from camera shake. This happens when the camera moves while the shutter is open, exposing the image sensor. Always try to steady the camera. Holding it with two hands and pressing the viewfinder gently against your face will help. You can also lean against something or use a tripod, a monopod, or even a beanbag to steady the camera.
You might also try reducing the effect of camera shake by selecting a fast shutter speed. This reduces the amount of time the image sensor is exposed to shaky conditions.
A helpful rule of thumb is to set your shutter speed to one over the focal length.
This means if the focal length of your lens is 300 millimeters, for example, you should set your shutter speed to at least 1/300 of a second. If the focal length is 30 millimeters, you might get by using a shutter speed as low as 1/30 of a second.
Let’s try practicing with different focusing modes and achieving optimal image sharpness.
Assignments
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Set your camera to continuous servo AF mode. Your camera will now continuously focus, since your subjects are moving. A sports game or a busy street would be an ideal place to practice with continuous mode. While you are capturing these images with the different focusing modes notice the parts of the image that are sharp and those that are not as clear.
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For experimentation purposes and more practice set your camera to a low shutter speed. Hold your camera without using a tripod and take a photograph of a person. Now, put your image on a tripod and capture the same image. Next, increase your shutter speed and take a picture of the same subject. Compare your last two shots to your first. The last two shots should appear sharper than the first image that was taken without a tripod and a low shutter speed