Mach bands

Mach bands or the Mach effect refers to an optical phenomenon from edge enhancement due to lateral inhibition of the retina 2. This is an inbuilt edge enhancement mechanism of the retina, where the edges of darker objects next to lighter objects will appear lighter and vice versa, creating a false shadow 4

This has been attributed as a source of diagnostic error in radiology:

Knowledge of the phenomenon may help prevent Mach bands being mistaken for a true abnormality such as pneumomediastinum.

History and etymology

Named after the Austrian physicist Ernst Waldfried Josef Wenzel Mach (1838-1916) who first described it in 1865 5.  


Article information

rID: 7804
Synonyms or Alternate Spellings:
  • Mach effect
  • Mach band

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Cases and figures

  • Figure 1: Mach effect (diagram)
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  • Case 1: mimicking pneumomediastinum
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  • Case 2: mimicking odontoid fracture
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  • Case 3: mimicking pneumomediastinum
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