This optical aberration is generally most visible as a coloring and lightening of dark edges adjacent to bright areas of broad-spectrum illumination, such as daylight or various types of gas-discharge lamps.
Lenses in general exhibit axial chromatic aberration, in which different colors of light do not focus in the same plane.
Normally, lens designs are optimized so that two or more (at least three for apochromatic lenses) wavelengths of light in the visible spectrum focus at the same plane.
Most film has relatively low sensitivity to colors outside the visible range, so light spread in the near ultraviolet (UV) or near infrared (IR) rarely has a significant impact on the image recorded.
[citation needed] Although the lens glass itself filters out much of the UV light, and all digital cameras designed for color photography incorporate filters to reduce red and IR sensitivity,[citation needed] the chromatic aberration can be sufficient for unfocused violet light to tint nearby dark regions of the image.