This raises a point that's been largely ignored in this thread: where does the reality of color lie?
If there is a *causal* effect between the spectrum of the light and the perceived color that is real.
If one "reliable" observer sees the same spectrum once as green and another as red. That is a perception (or mistakes/illusions). Not real. Those people who see the ballon purple will always say purple in response to that spectrum. That means "correct recognition" (no matter what is the internal representation: a "smell", a "taste", a "purple" object or whatsoever).
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BEHAVIORAL AND BRAIN SCIENCES(2003) 26,3–64
Printed in the United States of America
Color realism and color science
Alex Byrne Department of Linguistics and Philosophy, Massachusetts Institute of Technology
David R. Hilbert Department of Philosophy and Laboratory of Integrative Neuroscience, University of Illinois at Chicago
Abstract: The target article is an attempt to make some progress on the problem of color realism. Are objects colored? And what is the nature of the color properties? We defend the view that physical objects (for instance, tomatoes, radishes, and rubies) are colored, and that colors are physical properties, specifically, types of reflectance. This is probably a minority opinion, at least among color scientists.
Textbooks frequently claim that physical objects are not colored, and that the colors are “subjective” or “in the mind.” The article has two other purposes: First, to introduce an interdisciplinary audience to some distinctively philosophical tools that are useful in tackling the problem of color realism and, second, to clarify the various positions and central arguments in the debate.
The first part explains the problem of color realism and makes some useful distinctions. These distinctions are then used to expose various confusions that often prevent people from seeing that the issues are genuine and difficult, and that the problem of color realism ought to be of interest to anyone working in the field of color science. The second part explains the various leading answers to the problem of color realism, and (briefly) argues that all views other than our own have serious difficulties or are unmotivated. The third part explains and motivates our own view, that colors are types of reflectances and defends it against objections made in the recent literature that are often taken as fatal.
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Experiments show that starting at mesopic level there are hue and saturation shifts, errors sometimes, but the different wavelenghts are *recognized*. A color is identifyed more or less accurately depending on the illumination level (the amount of errors in hue and saturation are measured).
Starting at scotopic level there is no causal effect linking wavelenght to color. However there is a causal effect linking lightness and perceived color. We shifts gradually from the percetion of millions of colors with small errors in hue and saturation to few colors in the green-red scale, to green-red related to lightness. This progression and continuity is not casual: often (because of the purkjnie effect) the long wavelenghs are perceived as darker than the short wavelegths. Thus our cognitive system, which try to get the most probable color from *any* little bit of information, estimates *red* the dark patches and *green* the lightest.
This guess is often correct for many reflecting surfaces. It is not the same for surfaces emitting lights. In fact The medium lights in M42 are redder that the high lights and in this case the gues is (casually) correct. But the medium lights in M27 are green and the guess (they are seen reddish) is wrong.
If you see *red* the OIII M27 and *red* the ha in M42 you are not seeing the real color but the real lightness as a color.
You will probabl be able to see colors thrugh the OIII narrowband filter. Surprisingly, in an object is partly in the filter view and partly out, you also will see the correct color. But there is no doubt that your receptors are not providing a useful signal... but your cognitive system works around and in this case it arrives at a good guess.
The colors are not real, but correct. IN M27 the colors are not real and wrong. IN M42 they are probaly not real but correct.
The only way to know if real red is seen in M42 is to look at where ha in seen. If a region that looks red is not visible in Ha then that red is a brain artifact.
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