I am new to Lanczos filters and trying to figure out how they can be used to generate a zero-phase lowpass filter with good time-domain properties.
[This example](http://scitools.org.uk/iris/docs/v1.2/examples/graphics/SOI_filtering.html) shows how to implement such a filter in Python but does not give any justification for the choice of window length, despite it determining the filter order, which I would think a relatively important parameter. Also, I am not sure about its phase response.  

Does anyone have insights about the uses of Lanczos filters in this sort of context, their pros and cons, and how to choose the window size objectively?