It is also worth noting that these sorts of configurations are tremendous demonstrations that our conventional theory around HKE is likely rubbish; the experience of “brightness” or “lightness” has a dependency on our cognition arriving at inferred configurations, and the segmentation-decomposition-assignment process.

As such, there are *no models* that will properly arrive at “lightness” or “brightness” beyond what the minimally distinct boundary quantification of Munsell has already achieved.

In *equiluminant* cases, the chrominance vector is *greater than* the luminance vector.

Describing the cognition as “lighter” or “brighter” under this lens is impoverished.

Is there a *difference* in the qualia of the experience? Absolutely. But the description that we muster is often *detatched* from the obvious-in-hindsight-only is likely an attempt to summarize a proximity construct; a *spatial* description of what we are cognizing.

As such, “brightness” and “lightness” are poor terms.

I would suggest that our understanding of these gradients in chrominance and luminance are *incredibly* useful as tools to understand segmentation-decomposition-assignment frameworks.

The facts of the matter are that while it is easy to “see” something, it is far more challenging to identify the cognitive heuristics at work that construct this “sight idea”.

Chrominance and Luminance relationships appear to govern more than mere “colour”, as we can see in the attached example.

As the author, I

had zero “authorial intent” to partition the picture into a highly probably segmented form. In fact, *quite the opposite*.

I had originally asserted that each row was equipment under a belief that *luminance invariance* would be one dimension of mathematical continuity. The slope of the luminance gradient on each row is *zero*.

Yet note how chrominance continuity disrupts the local continuity, and segmentation leads to forms emerging.

But let’s go a step further…

If we have evidence here of chrominance variegation tipping the cognitive scales toward segmentation, can we suggest that luminance also does so?

The answer is *of course*, but the notion of a luminance discontinuity signifying a segmented boundary condition is not the question I am posing.

My question is whether similar polarity variegations are *also* segmenting the cognized Cartesian-like internal model?

This “step series” is a case in point.

It happens to be the bogus L star rate of change from CIE Lab, and frankly, such models are pure, unadulterated horse manure.

But we should meditate on this sample.

A few observations.

* Discontinuous local frameworks segment each “step”. C1 continuity.
* Global frameworks appear to have some form of continuity; the steps can be segmented “as a whole”, into a “continuous” form.
* Under a global framework, it is plausible to suggest that we have an

example of a little thought of segmentation, along a “distance from us” partitioning.

If we agree that segmentation is an almost subconscious partitioning of the two dimensions relative to us, is it not reasonable to suggest that while less obvious, the segmentation is “natively 2.5 or 3D-like”?

@troy_s

While each swatch may be the same luminance, the red swatch has four times the chrominance as the other pastel colors.

And going back to "its convenient to think of chroma as hue dependent luminance."

While Legge et alia found that (for reading) luminance contrast and chroma contrast are not "additive", as for lightness perception, can we say that Helmholtz-Kohlrausch effect is loosely:

L* + C = HKe

With C values multiplied with some magic number for an estimated concordance vs L* values.

or

L + max(a,b) = HKe

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The fact that high chroma colors look brighter, is perhaps stated as:

Other things being equal, "lightness perception is directly affected as the sum of the luminance channel and the chrominance channel."

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@Myndex Not sure where the four times comes from?

We can verify mathematically that the chrominance of any triplet is `max(RGB) = luminance(RGB) + chrominance(RGB)`.

This leads to the peculiar fact that the B carries tremendous chrominance, and low luminance. R is second, with G third.

Weakest angle is ~575nm.

The question of the “lustre” of “reds” seeming stronger remains one that is intriguing.

@troy_s

Okay, so in the normal eye, there are more L cones than any other. Stim the L cones only, with the L cones making up the majority of the luminance signal (with L cone peak being a greenish yellow).

And meanwhile the S cones are not contributors to the luminance channel (any luminance from the display blue primary is due to the stim of the M and L cones).

The sRGB red primary creates about 21% luminance.

The first image is a neutral grey of 21% luminance #868686 against #f00 .(equal Ys, 0 C vs red 104 C)

The second image is #f00 v #860000 (Lc25)

The third is #009494 vs #f00
(equal Ys — 33 C v 104 C)

The 4th is #d11 v #06f
(equal Ys & equal chroma)

Note: Ys is "screen luminance"

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Some very rough calcs:

#f00 mostly stims L cone to Ys=21.3%

#868686, the values are
R Ys= 4.5
G Ys=15.3
B Ys= 1.5

So #f00
L 16.6%
M 4.7%
L gets 3.5 x more than M

#868686
R
L cone 3.5%
M gets 1.0%,

G & B
Remaining 16.8%:
L 9.7%
M 8.9%
=
L for the Grey 13.2%
M for the Grey 9.9%

L 1.33 more than M