Mach Bands
What Are Photoreceptors?
What Is Lateral Inhibition?
How Does The Hermann Grid Work?
How Do Mach Bands Work?
What Are Light Contrasts?
How Does White's Illusion Work?
When looking at the Mach Bands it appears as if the color bands curve inward or that each band is a gradient, however, each band is a solid color. Each band reflects different amounts of light with the darker bands reflecting less and lighter bands reflecting more.
The light reflected from each band appears to change because of the position of some receptive fields. Within fields aimed directly in between or near the edges of bands, some parts detect light while other parts do not, causing a competitive reaction.
The image below shows various receptive fields lined up along the bands. Receptive field A is detecting the
least amount of light while field B is detecting the most.
The light photoreceptor center of receptive field D is positioned completely within the first darker band,
however its dark photoreceptor surround is partially within the second lighter band. As a result, the surround generates an
inhibitory reaction (lateral inhibition) making field D see a
darker area than other receptive fields positioned entirely in that same band (e.g., field A).
A similar phenomenon occurs with receptive field C. Its light photoreceptor center is within the lighter third band while its dark photoreceptor surround is partially within the darker middle band. The surround is generating an inhibitory reaction making field C see a lighter area than other receptive fields positioned entirely in that same band (e.g., field B).
Light Contrasts involves a similar phenomenon.