Farbsäumen

Farbsäumen, also known as chromatic aberration, is an optical phenomenon that occurs when a lens fails to focus all colors of light to the same point. This happens because different wavelengths of light refract at slightly different angles as they pass through a lens. As a result, a colored fringe or halo can appear around high-contrast edges in an image, particularly where bright objects meet dark backgrounds.

There are two main types of chromatic aberration: radial and axial. Radial chromatic aberration causes a magnification difference for different colors, leading to a barrel or pincushion distortion effect where colors spread out from the center or converge towards the edges. Axial chromatic aberration, on the other hand, causes different colors to focus at different distances along the optical axis, resulting in a blurred appearance where one color is in focus and others are not.

Farbsäumen are more noticeable with simpler lens designs and at wider apertures. High-quality lenses, especially those incorporating multiple elements made of different types of glass (such as achromatic or apochromatic lenses), are designed to minimize this effect by bringing different wavelengths of light closer to a common focal point. Digital image editing software can also be used to correct for chromatic aberration, often by shifting color channels to realign them. While often considered an undesirable artifact, in some artistic contexts, intentional chromatic aberration can be employed for creative effect.