Changes

The high-frequency cut-off represents the optical [[limitations]] of the visual system's ability to resolve detail and is typically about 60 cycles per degree. The high-frequency cut-off is related to the packing density of the retinal photoreceptor cells: a finer matrix can resolve finer gratings.

The high-frequency cut-off represents the optical [[limitations]] of the visual system's ability to resolve detail and is typically about 60 cycles per degree. The high-frequency cut-off is related to the packing density of the retinal photoreceptor cells: a finer matrix can resolve finer gratings.

The low frequency drop-off is due to lateral inhibition within the retinal ganglion cells. A typical retinal ganglion cell presents a centre region with either excitation or inhibition and a surround region with the opposite sign. By using coarse gratings, the bright bands fall on the inhibitory as well as the excitatory region of the ganglion cell resulting in [http://en.wikipedia.org/wiki/Lateral_inhibition lateral inhibition] and account for the low-frequency drop-off of the [http://en.wikipedia.org/wiki/Contrast_(vision)#Contrast_sensitivity human contrast sensitivity function].

The low frequency drop-off is due to lateral inhibition within the retinal ganglion cells. A typical retinal ganglion cell presents a centre region with either excitation or inhibition and a surround region with the opposite sign. By using coarse gratings, the bright bands fall on the inhibitory as well as the excitatory region of the ganglion cell resulting in [http://en.wikipedia.org/wiki/Lateral_inhibition lateral inhibition] and account for the low-frequency drop-off of the [http://en.wikipedia.org/wiki/Contrast_(vision)#Contrast_sensitivity human contrast sensitivity function].