Color errors in lenses

longitudinal color aberration

This causes the image position to vary for different wavelengths (colors) of light. Since the image sensor can only assume a certain position, this results in a blurred image. If two extreme wavelength ranges are used in succession, e.g. visible light and infrared radiation, either refocusing or a considerable loss of sharpness must be accepted. Figure 1 illustrates this.

Figure 1: The longitudinal color aberration

Lateral chromatic aberration

Lateral chromatic aberration manifests itself as a shift of the entire beam and thus of the pixel for different wavelengths (colors) of the radiation. For color cameras, this leads to colored stripes at the edges, and for black-and-white cameras, to blurred edges (Fig. 2).

Color aberrations can be reduced by using special optical glasses called "ultra low dispersion" glasses (more precisely, glasses with anomalous partial dispersion). 

Fig. 2: The lateral chromatic aberration