I cannot find out what does "notch" means in image processing? We have selective filters that one of the best of them is Notch filters. but what does the concept of "Notch"? why they are called "notch" filters?

  • $\begingroup$ Notch filter which rejects the certain range of frequencies in predefined neighborhoods about a center frequency.. In the image $\endgroup$
    – Prasanna
    Nov 7, 2017 at 4:23

1 Answer 1


In standard 1D signal processing, notch filters are filters that try to remove one specific frequency, and pass all others.

I say "try to" because this is not usually achievable, but it comes close.

Steve W. Smiths's DSP Guide has a nice plot (Figure 19.6b below) that shows the frequency response of such filters.

In image processing, it will be the same thing, but instead of a 1D filter it'll be a 2D filter probably comprised of two 1D notch filters --- one in each image direction.

enter image description here

  • $\begingroup$ What is the difference between a bandreject filter and notch filter, especially in image processing. $\endgroup$
    – maia
    Apr 19, 2021 at 17:39
  • $\begingroup$ @maia Ask that as a question! Notch == single frequency; band == range of frequencies. $\endgroup$
    – Peter K.
    Apr 19, 2021 at 17:48

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