EyeonTips:Manual/Fusion 6/Blur

From VFXPedia

This is a comparison of blur filters visualized as "cross-sections" of a filtered edge. As you can see, box will create a linear ramp, while Bartlett creates a somewhat smoother ramp. Multibox and Gaussian result in even smoother ramps that are virtually indistinguishable unless you zoom in really close on the slopes. As mentioned above, Gaussian will overshoot slightly and may result in negative values if used on floating point images.