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(a) Examples of nonfiltered scenes belonging to two different categories (outdoors and indoors) (b) Example of low-spatial frequency scenes (LSF) below 0.5 and 1 cycles per degree (cpd) and high-spatial frequency scenes (HSF) above 6 and 12 cpd. It should be noted that the perception of spatial frequencies may be affected by size reduction of the scenes for illustrative purposes.
