Defokus

Defokus, also known as defocus or out-of-focus, refers to a condition in photography and optics where the subject of an image is not sharply focused. This phenomenon occurs when the lens of a camera is not set to the correct focal distance for the subject, resulting in a blurred image. Defokus can be intentional, as in the case of creative effects such as bokeh or depth of field, or unintentional, often due to incorrect focusing or camera movement.

In photography, defokus can be used to draw attention to the subject by blurring the background, creating a shallow depth of field. This technique is commonly employed in portrait photography to isolate the subject from the surroundings. Conversely, a wide depth of field can be achieved by using a large aperture, which keeps both the subject and background in focus.

Defokus can also occur in optical systems, such as microscopes and telescopes, where the image plane is not aligned with the focal plane of the lens. This can result in blurred or distorted images, affecting the quality of observation or measurement.

In digital imaging, defokus can be corrected using software algorithms that analyze the image and adjust the focus accordingly. This process, known as autofocus or digital refocusing, allows photographers to improve the sharpness of their images after they have been taken.

Overall, defokus is a fundamental concept in photography and optics, with both creative and practical applications. Understanding the principles of defokus can help photographers and optical engineers achieve better results in their work.