<p>One interesting way to study transparency is by looking at cases where we perceive transparency even though there isn't any objective transparency.</p>

<p>Take this illusion from <a href="http://web.mit.edu/persci/people/adelson/pub_pdfs/gazzan.pdf" rel="nofollow noreferrer">Adelson (2000)</a> as an example.</p>

<p><img src="https://i.sstatic.net/C0Zor.jpg"></p>

<p>In the both panels the diamonds have the same physical brightness (pixel value on the monitor), but our perception of the diamonds on the right is warped by the seemingly-transparent dark stripe that covers the diamonds on the top. Thus, even low-level image features like brightness are perceptually warped by the way our brain perceives the structure of the image.</p>

<p>There are a large number of papers on mathematical models of illusory transparency perception. A starting point might be <a href="http://web.mit.edu/persci/people/bart/Perception_Neon.pdf" rel="nofollow noreferrer">Anderson (1997)</a> and the references within. But, the general message from this research is that we sometimes perceive transparency as the result of imposing some kind of higher-order structure to make sense of the image.</p>

CC BY-SA 3.0
2014-05-26T22:17:16.123Z
That's a great answer, I only wish it would address the question more directly. The answer offers support to the idea that transparency is a higher-level operation, thus cannot have its own channel.
Izhaki
CC BY-SA 4.0
2014-05-26T22:00:19.010Z
2019-01-04T18:32:21.870Z
2019-01-04T18:32:21.870Z
Josh
<p>Referring to (for example) <a href="http://rads.stackoverflow.com/amzn/click/0123708966" rel="nofollow">Visual Thinking for Design</a>, the book discusses various low-level processing channels in the brain. Colour and orientation are two examples.</p>

<p>I wonder if transparency is another such channel; and if it isn't, how exactly transparency manifests itself within the brain. </p>

CC BY-SA 3.0
2014-05-23T14:48:18.483Z
'low-level processing' is not a well defined term. Do you mean in V1 (primary visual cortex)? I think transparency is a higher-order feature that requires (object) boundary detection. I doubt you can see a big effect of it in the early visual processing where color and orientation are processed.
Memming
CC BY-SA 3.0
2014-05-23T16:50:56.100Z
That is exactly my thinking, I doubt it is decoded in V1. You could also argue that transparency requires some higher level comparisons, as it involves both colour comparison, and some form of mental subtraction - you can attribute a single colour to two different objects. It kind of follow that you cannot attribute to it the term 'channel' - it's higher level.
Izhaki
<vision>
Does transparency have its own visual channel?
Izhaki
# Does transparency have its own visual channel?

(Asked by: username_0 on 2014-05-20)

Referring to (for example) [Visual Thinking for Design](http://rads.stackoverflow.com/amzn/click/0123708966), the book discusses various low-level processing channels in the brain. Colour and orientation are two examples.

I wonder if transparency is another such channel; and if it isn't, how exactly transparency manifests itself within the brain.

**Tags:** vision

> **Comments:**
> **username_1**: 'low-level processing' is not a well defined term. Do you mean in V1 (primary visual cortex)? I think transparency is a higher-order feature that requires (object) boundary detection. I doubt you can see a big effect of it in the early visual processing where color and orientation are processed.  
> **username_0**: That is exactly my thinking, I doubt it is decoded in V1. You could also argue that transparency requires some higher level comparisons, as it involves both colour comparison, and some form of mental subtraction - you can attribute a single colour to two different objects. It kind of follow that you cannot attribute to it the term 'channel' - it's higher level.  

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## 1 answers

### Answer by username_2 on 2014-05-26. Score: 4

One interesting way to study transparency is by looking at cases where we perceive transparency even though there isn't any objective transparency.

Take this illusion from [Adelson (2000)](http://web.mit.edu/persci/people/adelson/pub_pdfs/gazzan.pdf) as an example.

![](https://i.sstatic.net/C0Zor.jpg)

In the both panels the diamonds have the same physical brightness (pixel value on the monitor), but our perception of the diamonds on the right is warped by the seemingly-transparent dark stripe that covers the diamonds on the top. Thus, even low-level image features like brightness are perceptually warped by the way our brain perceives the structure of the image.

There are a large number of papers on mathematical models of illusory transparency perception. A starting point might be [Anderson (1997)](http://web.mit.edu/persci/people/bart/Perception_Neon.pdf) and the references within. But, the general message from this research is that we sometimes perceive transparency as the result of imposing some kind of higher-order structure to make sense of the image.

> **Comments:**
> **username_0**: That's a great answer, I only wish it would address the question more directly. The answer offers support to the idea that transparency is a higher-level operation, thus cannot have its own channel.  

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