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Butterworth smoothing filter six curves by different f c and n parameters (equation (2)). A, B, C curves created by critical frequency f c = 0.1 c/pixel and order n equal to 2, 8, 32 correspondingly. D, E, F curves created by critical frequency f c = 0.3 c/pixel and order n equal to 2, 8, 32 similarly [6].
