Sharpness Isn't Everything
Shallow depth of field can focus attention on a foreground subject by making the background less sharp.
Your photos don't always have to be sharp to be effective. In many cases, it's better to have part of the scene sharper than the rest. Your pictures can be sharp or unsharp in different ways. The first way concerns motion. Several factors affect the way motion is captured in images. These include your image sensor's speed, the overall brightness of the scene, lens focal length, and subject speed, direction, and distance. Another kind of sharpness concerns depth of field, how much of the scene will be sharp in the image. Even if you are photographing a static scene, part may not be sharp in the picture if you do not have enough depth of field. However, a shallow depth of field can be used to make a busy background less distracting by having it out of focus in the picture.
Motion in a scene can be frozen or blurred
depending on the shutter speed and other factors. Blur can be used creatively to evoke a feeling of motion as in this shot of a waterfall in Yosemite National Park.