Question

Butterworth lowpass filter has a parameter, filter order, determining its functionality as very sharp or very smooth filter function or an intermediate filter function. If the parameter value is of lower order, the filter approaches to which of the following filter(s)?

(a) Ideal lowpass filter

(b) Gaussian lowpass filter

(c) All of the mentioned

(d) None of the mentioned

I have been asked this question during an internship interview.

My doubt stems from Smoothing Frequency-Domain Filters topic in division Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

The correct choice is (b) Gaussian lowpass filter

Explanation: For high value of filter order Butterworth lowpass filter behaves as Ideal lowpass filter, while for lower order value it has a smoother form behaving like Gaussian lowpass filter.