Fig. 3
From: Registration of retinal sequences from new video-ophthalmoscopic camera
Images a, b show averaged spectra computed from one whole sequence: a spectrum from original sequence and b spectrum from 3 × 3 pixel median-filtered sequence (frame-by-frame). Image c shows spectral difference—the dark values in the middle represent “no change” around low frequencies, and the grey levels at higher frequencies represent reduced spectral components in median-filtered frames