Fookuskaugusega

Fookuskaugusega, known in English as focal length, is a fundamental concept in optics that describes the distance between a lens's optical center and its focal point, where light rays converge or appear to diverge after passing through the lens. It is typically measured in millimeters (mm). The focal length determines the lens's magnifying power and the field of view it provides, influencing how an image is captured or viewed.

In camera optics, a short focal length (wide-angle lens) produces a broader field of view, making it ideal for capturing landscapes or large groups. Conversely, a long focal length (telephoto lens) narrows the field of view and magnifies distant objects, which is useful in portrait or wildlife photography. The focal length also affects the perspective and depth of field within an image.

Focal length can be categorized as fixed or variable. Fixed lenses have a single focal length, such as 50mm or 85mm, while zoom lenses offer a range of focal lengths, like 24-70mm. In optical systems, the focal length is related to the curvature of the lens: more curved surfaces generally result in shorter focal lengths.

The concept of focal length extends beyond photography to areas including astronomy, microscopy, and optical engineering, where it helps describe how lenses focus light to form clear images. Understanding the focal length is essential for selecting appropriate optical devices and achieving desired imaging effects.