Repeat edge pixels on blur filters?

Hi Ben, thanks for the response. As you probably know when blurring you average a pixels value to those surrounding it. When you get to the edge of the image there is of course nothing to average to, so you usually get a dull border that appears. In things like After Effects and FXFactory the blur will repeat the pixels at the edge so that the value doesn't suddenly drop, thus avoiding the dull border.

I've just now realised that Motion uses a crop to achieve the same effect, but it doesn't always work. It works on the gaussian blur, for example, but not on the defocus one.