The effects of low-pass filtering on spectral power.

<p>Power spectra in 800 frequency bins were computed for the unfiltered images used in Experiment 2, and compared to power spectra of the Gaussian filtered images used in Experiment 3. The median difference in power per bin is plotted. This shows that seventy-five percent of the difference is accounted for in frequency bins between 0.2 and 0.67 cycles per degree (left of vertical dashed line). The power does not differ significantly in the range 0 to 0.19 cycles per degree (small red circles).