Chromatic Focal Shift
Shift in back focal length with respect to the primary wavelength
Maximum Shift The maximum extent in lens units for the horizontal axis. The vertical axis scale is set by the range of wavelengths defined. Enter zero for automatic.
Pupil Zone The radial zone in the pupil used to compute the back focus. The default value of zero means a paraxial ray will be used. Values between 0 and 1 mean real marginal rays are used in the appropriate zone in the entrance pupil. A 1 is at the edge of the pupil, or full aperture.
Discussion This is a plot of the shift in back focal length with respect to the primary wavelength. At each plotted wavelength, the shift in image space required to reach focus for that color marginal ray is computed. The shift distance is computed in the same media (glass or air) as the surface prior to the image surface. This plot may not be meaningful for non-paraxial systems.
The maximum shift setting overrides the default scaling. Units are in lens units. The entire plot is always referenced to the primary wavelength paraxial focus. The diffraction limited depth of focus listed is given by the formula 4λF2, where F is the working F/# and λ is the primary wavelength
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