How does zero-padding affect the magnitude of the DFT?

You can interpolate the DFT by zero padding. Zero padding enables you to obtain more accurate amplitude estimates of resolvable signal components. On the other hand, zero padding does not improve the spectral (frequency) resolution of the DFT. The resolution is determined by the number of samples and the sample rate.

1. What is the effect of zero padding in frequency domain?
2. How does zero padding affect FFT?
3. Does zero padding increase frequency resolution?
4. Why zero padding is done on the image before computing its discrete Fourier transform?

What is the effect of zero padding in frequency domain?

In this case, we can say “zero padding in the frequency domain results in an increased sampling rate in the time domain”.

How does zero padding affect FFT?

Zero padding allows one to use a longer FFT, which will produce a longer FFT result vector. A longer FFT result has more frequency bins that are more closely spaced in frequency.

Does zero padding increase frequency resolution?

In summary, the use of zero-padding corresponds to the time-limited assumption for the data frame, and more zero-padding yields denser interpolation of the frequency samples around the unit circle. Sometimes people will say that zero-padding in the time domain yields higher spectral resolution in the frequency domain.

Why zero padding is done on the image before computing its discrete Fourier transform?

Zero padding in the time domain is used extensively in practice to compute heavily interpolated spectra by taking the DFT of the zero-padded signal. Such spectral interpolation is ideal when the original signal is time limited (nonzero only over some finite duration spanned by the orignal samples).