Mach bands is an optical illusion named after the physicist Ernst Mach. It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they contact one another, by triggering edge-detection in the human visual system.
Exaggerated contrast between edges of the slightly differing shades of gray appears as soon as they touchAlong the boundary between adjacent shades of grey in the Mach bands illusion, lateral inhibition makes the darker area falsely appear even darker and the lighter area falsely appear even lighter.
The Mach bands effect is due to the spatial high-boost filtering performed by the human visual system on the luminance channel of the image captured by the retina. Mach reported the effect in 1865, conjecturing that filtering is performed in the retina itself, by lateral inhibition among its neurons.[1] This conjecture is supported by observations on other (non-visual) senses, as pointed out by von Békésy.[2] The visual pattern is often found on curved surfaces subject to a particular, naturally-occurring illumination, so the occurrence of filtering can be explained as the result of learnt image statistics. The effect of filtering can be modeled as a convolution between a trapezoidal function that describes the illumination and one or more bandpass filters. A tight approximation is obtained by a model employing 9 even-symmetric filters scaled at octave intervals.[3]
The effect is independent of the orientation of the boundary.
In radiologyedit
An illusory cross (×) appears in the large image due to gradient discontinuity[4]
This visual phenomenon is important to keep in mind when evaluating dental radiographs for evidence of decay, in which grayscale images of teeth and bone are analyzed for abnormal variances of density. A false-positive radiological diagnosis of dental caries can easily arise if the practitioner does not take into account the likelihood of this illusion. Mach bands manifest adjacent to metal restorations or appliances[citation needed] and the boundary between enamel and dentin.[5] Mach bands may also result in the misdiagnosis of horizontal root fractures because of the differing radiographic intensities of tooth and bone.[6]
Mach effect can also lead to an erroneous diagnosis of pneumothorax by creating a dark line at the lung periphery (whereas a true pneumothorax will have a white pleural line).[7]
In computer graphicsedit
Example of Mach bands at the ends of gradients where the derivative of the luminance is discontinuous
Actual luminance profile
Perceived luminance profile
Smooth luminance profile for comparison
Mach bands can also appear when there is a discontinuity in the derivative of a gradient, a visual effect common when intensities are linearly interpolated such as in Gouraud shading.
Computer image processing systems use edge-detection in a way analogous to the brain, using unsharp masking to clarify edges in photos for example.
^Ratliff, Floyd (1965). Mach bands: quantitative studies on neural networks in the retina. Holden-Day. ISBN9780816270453.
^von Békésy, Georg (1967). "Mach Band Type Lateral Inhibition in Different Sense Organs" (PDF).
^Frederick A. A. Kingdom (4 November 2014). "Mach bands explained by response normalization". Frontiers in Human Neuroscience. 8: 843. doi:10.3389/fnhum.2014.00843. ISSN 1662-5161. PMC4219435. PMID 25408643.
^P. Ambalathankandy et al, Radiography Contrast Enhancement: Smoothed LHE Filter a Practical Solution for Digital X-Rays with Mach Band, 2019 Digital Image Computing: Techniques and Applications
^Devlin, Hugh. Operative Dentistry: A Practical Guide to Recent Innovations, Springer 2006 ISBN978-3-540-29616-4 page 11
^Nielsen, Christen J.; "Effect of Scenario and Experience on Interpretation of Mach Bands," Journal of endodontics Volume 27, Issue 11, Pages 687–691
^Parker, M. S.; Chasen, M. H.; Paul, N. (2009). "Radiologic Signs in Thoracic Imaging: Case-Based Review and Self-Assessment Module". American Journal of Roentgenology. 192 (3_Supplement): S34-48. doi:10.2214/AJR.07.7081. PMID 19234288. S2CID 34785665.
Mach Band figure and explanatory hypothesis, Laboratory of Dale Purves
January 01, 1970
mach, bands, shock, wave, pattern, mach, diamond, optical, illusion, named, after, physicist, ernst, mach, exaggerates, contrast, between, edges, slightly, differing, shades, gray, soon, they, contact, another, triggering, edge, detection, human, visual, syste. For the shock wave pattern see Mach diamond Mach bands is an optical illusion named after the physicist Ernst Mach It exaggerates the contrast between edges of the slightly differing shades of gray as soon as they contact one another by triggering edge detection in the human visual system Exaggerated contrast between edges of the slightly differing shades of gray appears as soon as they touch Along the boundary between adjacent shades of grey in the Mach bands illusion lateral inhibition makes the darker area falsely appear even darker and the lighter area falsely appear even lighter Contents 1 Explanation 2 In radiology 3 In computer graphics 4 See also 5 References 6 Further reading 7 External linksExplanation editThe Mach bands effect is due to the spatial high boost filtering performed by the human visual system on the luminance channel of the image captured by the retina Mach reported the effect in 1865 conjecturing that filtering is performed in the retina itself by lateral inhibition among its neurons 1 This conjecture is supported by observations on other non visual senses as pointed out by von Bekesy 2 The visual pattern is often found on curved surfaces subject to a particular naturally occurring illumination so the occurrence of filtering can be explained as the result of learnt image statistics The effect of filtering can be modeled as a convolution between a trapezoidal function that describes the illumination and one or more bandpass filters A tight approximation is obtained by a model employing 9 even symmetric filters scaled at octave intervals 3 The effect is independent of the orientation of the boundary In radiology edit nbsp An illusory cross appears in the large image due to gradient discontinuity 4 This visual phenomenon is important to keep in mind when evaluating dental radiographs for evidence of decay in which grayscale images of teeth and bone are analyzed for abnormal variances of density A false positive radiological diagnosis of dental caries can easily arise if the practitioner does not take into account the likelihood of this illusion Mach bands manifest adjacent to metal restorations or appliances citation needed and the boundary between enamel and dentin 5 Mach bands may also result in the misdiagnosis of horizontal root fractures because of the differing radiographic intensities of tooth and bone 6 Mach effect can also lead to an erroneous diagnosis of pneumothorax by creating a dark line at the lung periphery whereas a true pneumothorax will have a white pleural line 7 In computer graphics edit nbsp Example of Mach bands at the ends of gradients where the derivative of the luminance is discontinuous Actual luminance profilePerceived luminance profileSmooth luminance profile for comparison Mach bands can also appear when there is a discontinuity in the derivative of a gradient a visual effect common when intensities are linearly interpolated such as in Gouraud shading Computer image processing systems use edge detection in a way analogous to the brain using unsharp masking to clarify edges in photos for example See also editAcutance Cornsweet illusion Hermann grid illusion Lateral inhibition Optical illusions Watercolour illusion Gibbs phenomenonReferences edit Ratliff Floyd 1965 Mach bands quantitative studies on neural networks in the retina Holden Day ISBN 9780816270453 von Bekesy Georg 1967 Mach Band Type Lateral Inhibition in Different Sense Organs PDF Frederick A A Kingdom 4 November 2014 Mach bands explained by response normalization Frontiers in Human Neuroscience 8 843 doi 10 3389 fnhum 2014 00843 ISSN 1662 5161 PMC 4219435 PMID 25408643 P Ambalathankandy et al Radiography Contrast Enhancement Smoothed LHE Filter a Practical Solution for Digital X Rays with Mach Band 2019 Digital Image Computing Techniques and Applications Devlin Hugh Operative Dentistry A Practical Guide to Recent Innovations Springer 2006 ISBN 978 3 540 29616 4 page 11 Nielsen Christen J Effect of Scenario and Experience on Interpretation of Mach Bands Journal of endodontics Volume 27 Issue 11 Pages 687 691 Parker M S Chasen M H Paul N 2009 Radiologic Signs in Thoracic Imaging Case Based Review and Self Assessment Module American Journal of Roentgenology 192 3 Supplement S34 48 doi 10 2214 AJR 07 7081 PMID 19234288 S2CID 34785665 Further reading editLotto RB Williams SM Purves D 1999 Mach bands as empirically derived associations Proceedings of the National Academy of Sciences 96 9 5245 50 Bibcode 1999PNAS 96 5245L doi 10 1073 pnas 96 9 5245 PMC 21849 PMID 10220451 Eagleman DM 2001 Visual Illusions and Neurobiology Nature Reviews Neuroscience 2 12 920 6 External links edit nbsp Wikimedia Commons has media related to Mach bands Demonstration of the Mach band was at NIST until July 2016 Mach Band figure and explanatory hypothesis Laboratory of Dale Purves Retrieved from https en wikipedia org w index php title Mach bands amp oldid 1185916305, wikipedia, wiki, book, books, library,
