# Filter Type

The Caliper tool supports a filter kernel that approximates the negative of the first derivative of a Gaussian distribution. This kernel provides better smoothing than traditional boxcar filters.

You specify the half-width of the filter, where the half-width is equal to four times the sigma of the Gaussian distribution. The following figure illustrates how you specify the width of the filter.

The filter itself is constructed by taking the negative of the first derivative of the Gaussian curve, as shown in the following figure.