Chromatic Aberration
An optical defect where a lens focuses different wavelengths of light at different points, causing color fringing or misregistration. Classified into longitudinal and lateral types.
Chromatic aberration (CA) is an optical defect from glass dispersion causing different wavelengths to refract at different angles. Shorter wavelengths (blue) refract more than longer ones (red), misaligning focal points and producing colored fringing along high-contrast edges.
CA is classified into two types requiring different correction approaches.
- Longitudinal (axial) CA: Wavelengths focus at different distances along the optical axis. Produces purple/green fringing at wide apertures. Stopping down 2-3 stops reduces it
- Lateral (transverse) CA: Wavelengths produce different magnifications. Invisible at center, increasing toward periphery. Stopping down does not help
- Optical correction: ED glass, fluorite, and achromatic designs minimize wavelength focal differences. APO lenses correct for three or more wavelengths
- Digital correction: RAW processors scale
RandBchannels to matchGchannel registration, eliminating lateral CA
Camera calibration in computer vision estimates CA parameters alongside distortion coefficients. Astrophotography and architectural photography demand meticulous correction due to abundant high-contrast edges.