Color fringing at contrast edges — different wavelengths are refracted at different angles.
White light consists of different colors, which a glass element refracts to varying degrees. The result: red, green, and blue do not meet at precisely the same point on the sensor. This becomes visible as magenta or green fringes on hard contrast edges — a branch against a bright sky is the classic stress test.
Longitudinal vs. Lateral
Longitudinal CA appears as colored blur in front of and behind the focus point. Lateral CA shows color fringes at the image edges. Modern apochromatic lenses (APO) correct both — but at a corresponding cost.
Creative Use
With vintage glass like the Helios 44-2 or Canon FD, CA is part of the character. The slight color fringes give the image an organic softness that many DoPs deliberately seek.
Related terms
Quiz
1. Zu welchem Department gehört „Chromatische Aberration"?