Talk:Mach bands

Is Mach bands also this?

I thought that 'Mach bands' referred to the image seen here (http://www.nku.edu/~issues/illusions/MachBands.htm) . In which gradients are illusory, is this a misnomer or are both Mach bands? --131.111.214.106 (talk) 11:44, 25 May 2010 (UTC)

lateral inhibition- explanation

Our brain see the image as a collection of vertical lines (because the gradient is horizontal). Every stripe has a value but the brain calculates the contrast of a stripe oppose to its neighbour stripes. That's why the stripes in edges of the gradient looks as if they are brighter or darker than their real value, they have less inhibition than the stripes in the uniform area.

This is appropriate for the article; will you provide a source? Hilarleo ^Hey,L.E.O.v 19:32, 6 March 2009 (UTC)

Where's the second 'explanation'?

horizontal cells

It could equally be caused by localised contrast enhancement due to the horizontal cells.

https://nba.uth.tmc.edu/neuroscience/m/s2/chapter14.html — Preceding unsigned comment added by BioImages2000 (talk • contribs) 10:09, 14 July 2022 (UTC)

Eye or brain?

Why should the lead state "The human eye sees..."- This illusion is not an ocular artifact; This phrase is a colloquialism. Unless we specify the precise areas of the brain/CNS actually involved in producing the effect, it is more accurate to say the human individual perceives... barring any other species also being shown to perceive 'lateral inhibition', that is. Hilarleo ^Hey,L.E.O.v 19:50, 6 March 2009 (UTC)

AFAIK, this effect arises because of spatial filtering done in the retina itself, before the image gets sent to the brain. --Jorge Stolfi (talk) 17:04, 26 November 2009 (UTC)

I believe, but have no evidence, that this is true. I believe that because similar edge effects are known to occur in film because of developer or collection point depletion at edges. Ehusman (talk) 01:13, 25 March 2013 (UTC)

I don't think it occurs in the retina. I had to look up an explanation of this "illusion" because I couldn't actually see it. However, I can force myself to see it if I try. Seems neuro to me. 24.147.151.253 (talk) 20:10, 13 September 2015 (UTC)

copyright violation

This article seems to contain large portions of text from http://www.purveslab.net/research/explanation/brightness/mach.html. That website claims that it's content is Copyright 2005 "All Rights Reserved", so unless anyone can show that this material is in the public domain, I'm afraid some major editing or deleting will be necessary (sorry) Andrewjuren(talk) 21:05, 15 April 2006 (UTC)

Why not take this image http://de.wikipedia.org/w/index.php?title=Bild:Maschsche_Streifen.svg ? --88.70.3.20 (talk) 20:31, 23 October 2008 (UTC)

Strange opener

An alternative explanation is that our visual perception, in using a fundamentally statistical strategy, represents the common occurrence of highlights and lowlights in association with luminance gradients.

Let's leave this here until someone can do something better with it. And that should include a source. DRosenbach ^{(Talk | Contribs)} 18:24, 22 June 2009 (UTC)

Perception topic

I've just added the {{Generalize}} tag to this, along with the above banners, because this is a perceptual phenomenon discussed in every 1st year psychology textbook or course, along with any neuroscience course, and, of course, perception!!! — Skittleys (talk) 13:45, 19 September 2009 (UTC)

IMHO "optical illusion" is a perfectly adequate classification. It is not a "narrow" or "specialized" view: I cnnot think of any aspect of Mach bands (including its neurological explanation) that would lie outside the topic "optical illusions" Nothing against having links somewhere to perception and neuroscience (perhaps in the "explanation" section); but "perceptual phenomenon" is a much broader subject (covers all senses, for one thing), and neuroscience is vastly broader still. Then why not claim that this is related to "zoology" and "biology" too? --Jorge Stolfi (talk) 17:16, 26 November 2009 (UTC)

Evolutionary psychology topic

I agree with both users, namely with Skittleys claiming it's a perceptual phenomenon, on one hand, and with Jorge Stolfi that it doesn't lie outside the topic "optical illusions", on the other hand. I'd like to add that this optical illusion, however, is not disability, but serves an important function which during the evolution helped those with the mutation to be able to recognize patterns better and faster because the borders between different shades of gray were exaggerated by this illusion. --DancingPhilosopher ^{my talk} 15:22, 27 November 2012 (UTC)

Mach bands in radiology - wrong efffect?

The section "Mach bands in radiology" seems to discuss a different pehnomenon. It talks about the light and dark bands that appear next to a sudden step in *lightness* level. But the whole point of the Mach bands illusion is that the bands appear even when there is no discontinuity in the *lightness level*, as long as the *lightness gradient* changes abruptly. I have seen the names "step effect" or "step illusion" used for the bands mentioned in that section. Is there a more specific name for those bands? --Jorge Stolfi (talk) 17:29, 26 November 2009 (UTC)

Mach bands are illusory, while the bands of differing contrast illustrated in the example are real lightness differences (that is, real changes in the image intensity due to the measuring device). It is a poor illustration of the described illusory phenomenon, so the image has been removed. FerrousCathode (talk) 12:15, 6 June 2013 (UTC)

Anyone else see boundary movement?

I'm open to the possibility that very few others might see this, but I notice the boundary area moving from right to left in the first image and from top to bottom in the lower. In other words I perceive the boundary line slowly moving from the darker area toward the lighter area, eventhough I know its not really happening. Anyone else seeing this? Some illusions don't work for everyone. Just wondering how common or rare what I'm seeing is. Racerx11 (talk) 04:21, 28 March 2010 (UTC)

Image

Does the image The Mach bands illusion correspond to this type of phenomenon or to an effect of unsharp masking ? In my opinion a better illustration is found into the external link Demonstration of the Mach band. Sorry for my poor english. —Preceding unsigned comment added by 90.36.181.18 (talk) 14:46, 17 May 2010 (UTC)

Clean-up?

The first image has a caption that describes it has having two regions of uniform brightness, white and black respectively. The regions in the image are clearly not white and black, but shades of grey. What was meant here, or has the image changed?

In the 'explanations' section, the article starts talking about a spinning disk that hasn't been described or pictured in the article. What's going on there? 82.24.248.137 (talk) 10:26, 11 August 2010 (UTC)

Red Line?

Why is there a red dotted line on the first image? 71.196.247.245 (talk) 16:57, 11 December 2012 (UTC)

The red dotted line marks the width of the illusionary Bands

Marking the width of the illusionary Mach Bands

--DancingPhilosopher ^{my talk} 14:52, 12 December 2012 (UTC)

Not to my eyes it doesn't, and I'd wager that it's heavily dependent upon the perceived contrast (both display hardware and lighting conditions) of the viewer. 138.38.24.108 (talk) 15:28, 6 August 2013 (UTC)

Adding Material

I think it would be beneficial to this article if someone elaborated on the explanation/introduction. I also feel this article needs more that just one other section. I would like to include some background information about Mach bands and then how they are used in the study of Sensory and Perception. Jgrady328 (talk) 00:00, 26 February 2013 (UTC)

What am I supposed to be looking at?

The article doesn't bother to tell me.--86.185.156.124 (talk) 03:58, 1 September 2013 (UTC)

Widespread inaccurate use in radiology

A lot of radiology textbooks and radiologists talk about the mach band phenomena in relation to x-rays. However, all of these cases are actual differences in image contrast at boundaries. For example if an image with a contrast boundary is magnified, the size of the mach band effect will stay the exact same while the objects in the image are enlarged. If the supposed "mach band" enlarges also, then it is an actual contrast difference in the image.

Lots of x-rays contain bands of different contrast at object boundaries and references always call these the "mach band" effect but they are incorrect because these bands enlarge when the image is enlarged. Does anyone know the real name for this phenomenon on x-rays?

I believe that the underlying topic is just that human vision perception will tend to exaggerate shade differences for adjacent areas. And a part of this effect is that portions of the image near the boundary appear to shift in shade. When the boundary is a line, then the shift in shade looks like a band. By the time a human looks at an X-Ray image, it is just an image (on a monitor, screen, film etc.) and so there is no reason that this effect wouldn't happen on an image that came from an X-Ray. So IMO a statement that excludes that would be wrong.

Your description seems to be of banding actually existing in the image. I've not seen that, (nor do I know of a name for it)) but if it is so, then there would be two types on banding on X-ray images. North8000 (talk) 21:28, 14 March 2014 (UTC)

what am i supposed to see

the article still doesnt help a lot, ie it hardly describes the nature of the (illusion) seen by people which results in that if i dont already know what it looks like (havent been shown before by someone), then just reading the article is not very helpful. it does a good job explaining why the illusion arises, but i belive it should desribe the illusion better before that. this part of the above comment (by North8000 (talk) 21:28, 14 March 2014 (UTC)):

"the underlying topic is just that human vision perception will tend to exaggerate shade differences for adjacent areas. And a part of this effect is that portions of the image near the boundary appear to shift in shade. When the boundary is a line, then the shift in shade looks like a band. "

seems like a good description to add to the lede in order to make it more informative. 89.134.199.32 (talk) 22:48, 6 February 2019 (UTC).