Mach Bands



Warning: this is a somewhat subtle effect for “vision insiders”.


What to see


On the top there is a dark area and a light area, the gap filled by a luminance ramp. The luminance ramp goes up, and then stays constant (visible in the green profile). The visual impression, however, is a bright band a the right end of the ramp, and a darkish band a the left end of the ramp (the latter being less pronounced).


What to do


The sliders allow to control the width of the ram and the luminance contrast. I find it surprising how shallow the ramp can be with the Mach Band remaining visible.




Mach Bands are old hat, I mean, 1865, really! And to boot, I always found them lame. A recent publication (Wallis & Georgeson 2012) prompted me to re-examine. Yes, it's weak, but interesting all the same.


The explanation is classically linked to preprocessing of the visual input in the retina (lateral inhibition). That is not really wrong, but the details are markedly more involved, see Wallis & Georgeson for a current in-depth account.




Mach E (1865) Über die Wirkung der räumlichen Verteilung des Lichtreizes auf die Netzhaut [On the effect of the spatial distribution of the light stimulus on the retina]. Sitzungsberichte der mathematischnaturwissenschaftlichen Classe der kaiserlichen Akademie der Wissenschaften 52:303–322

Wallis SA, Gerogeson MA (2012) Mach bands and multiscale models of spatial vision: The role of first, second, and third derivative operators in encoding bars and edges. Journal of Vision (2012) 12(13):18, 1–25



Created: 2013-01-19

Last update: 2013-10-04