Fokusebene

Fokusebene is a term used in optics and imaging to denote the plane in which an image is most sharply formed by a lens system. In practice, it refers to the image plane where rays from a point in the scene converge to a point, producing a sharp impression on the recording medium or sensor.

The word combines Fokus (focus) and Ebene (plane or level) in German. In English-language optics literature, the concept is commonly described as the focal plane or plane of best focus. The term is used in photography, microscopy, and vision science to indicate the intended plane of sharpness for a given focus setting.

When the focus is adjusted, the relative position of the camera's image plane changes with respect to the lens, so that a particular subject distance lies on the plane of best focus. Objects on that plane render with maximum sharpness, while objects at other distances appear progressively blurrier. The range of acceptable sharpness is known as the depth of field.

Applications of the concept include camera design and operation, where precise placement of the sensor or film is essential; microscopy, where the focal plane can be moved to study different depths within a specimen; and projection or cinema, where aligning the focal plane ensures crisp imaging on a screen or detector.

Related concepts include the focal plane, depth of field, focal length, and the image plane.