Re: perceptual differences in Lab deltaE
Re: perceptual differences in Lab deltaE
- Subject: Re: perceptual differences in Lab deltaE
- From: Andrew Rodney via colorsync-users <email@hidden>
- Date: Tue, 7 Jan 2020 13:06:08 -0700
> On Jan 7, 2020, at 12:31 PM, Wire ~ via colorsync-users
> <email@hidden> wrote:
>
> On Tue, Jan 7, 2020 at 04:14 Roger Breton via colorsync-users <
> email@hidden> wrote:
>
>> Hi Simon,
>>
>> [...] I'm curious how were you able to print chart patches with as little
>> as 0.3 deltaE (which flavor?) color differences... Suppose I was to
>> replicate your findings with my students?
>>
>> Best / Roger
>>
>> -----Original Message-----
>> From: colorsync-users <colorsync-users-bounces+graxx=
>> email@hidden> On Behalf Of simon--- via colorsync-users
>> Sent: Tuesday, January 7, 2020 5:48 AM
>> To: Roger Breton via colorsync-users <email@hidden>
>> Subject: perceptual differences in Lab deltaE
>>
>> Hi Andrew,
>>
>> I did some tests a few years ago by printing charts patches to exhibit
>> small deltaE variations.
>
>
> Ah Roger, I see why you posed the original query re billions of colors:
> you're an instructor!
>
> And I found the gap with Andrew...
>
> Roger begged the question "only so many colors are useful," which Andrew
> seized as hinging on a definition of the term color. Seems fair.
>
> The discussion fractured between Andrew's reframing "color" to mean a
> uniformly perceptually distinguishable difference under CIE vs my point
> that the gear industry brags about capability to produce a range of
> stimuli.
It's not just my definition, it's Fairchild, Giorgianni and Madden, GATF,
Sharma and many other experts in the field of color.
> The question Roger posed was directly in context of assessing display
> performance, so by my reckoning the claim of "millions" or "billions" is
> understood in that context as a device capability.
Millions and billions of numbers based on encoding, not necessarily colors. But
we've been over this too many times. You appear not to have connected those
dots and find this all circular.
> The perceptual factors
> are much more complex and subsumed by the device physics under ICC.
Try the CIE which predates ICC by a very, very long time.
> To drill into this a little further: We know that the device is built to
> the tri-stimulus model, and varies its output in a roughly linear response
> to data on its inputs. Whether anyone can or cares to see the output
> needn't be considered given the electro-mechanical basis of the device:
> three primaries, intensity controlled as individual channels (guns) and
> mixed through an aperture in direct proportion to the input channel data
> values. As it is well-known with such devices to be useful to go higher
> than 8 bpc to avoid certain rendering artifacts — regardless of other
> aspects of waste in the data format — and because the system physics are
> linear WRT inputs, aaannd as the inputs are numerical supporting millions
> or billions of combinations, we arrive at a euphemism of a count of colors,
> which seems to me wholly appropriate and fair. If you want to know what
> color and count really mean, further study the device.
>
> Andrew seized on the term "color" and re-contextualized it for reasons I
> don't quite follow, reframing device color as a count of discernible
> regions within the CIE spectrum locus according to some dE threshold
> criteria.
It's not just my definition, it's Fairchild, Giorgianni and Madden, GATF,
Sharma and many others.
> Sure it seems like an interesting way to count colors.
I know of no definitive counting of such colors perceived by the Standard
Observer and told you it's up to debate and ranges from somewhere between 7 and
12 million. But again, I know of NO ONE including you, that states it's 16.7
million.
> And it's the way ICC colorimetry works!
You're still confused about the ICC and Colorimetry.
> So ok fair enough. But what does it have to do with the original question in
> context of display vendor claims?
They claim billions of colors and we can't see billions of colors. The claim is
bogus.
> Don't we
> use tools like DisplayCal to just run gamut plots normalizing device
> numbers are to generic device spaces.
Humans (and cameras and scanners) do not have a color gamut.
> Andrew likes ProPhoto, the web likes sRGB, the device does Adobe, etc.
I don't know how you come up with such conclusions outside of assuming.
I don't "like" any specific RGB working space per se. If there were a prefect
RGB working space, we'd all use one.
The web doesn't 'like' sRGB. In fact, with a color managed browser, ANY RGB
working space will work as they do in color managed applications. The web isn’t
sRGB. Many users on the web don't have color managed browsers and use sRGB
gamut displays so viewing sRGB is the best of a bad situation (a lack of color
management). And sRGB is far, far more than just a color gamut.
> The plots tell us how well the specific
> display fits as a simplified percentage or let us look at detailed
> differences. And so on... Well, to the extent that the device adheres to a
> standard color space, which is now common, the input data format can be
> considered to be a literal count of colors within that space, according to
> explicit CIE criteria!
I don't know what makes you believe that some display that may have an sRGB
color gamut is outputting sRGB as specified. If that were true (and its not)
people wouldn't have to calibrate and profile their displays; they would all
equal sRGB out. They don't.
> Andrew's deal about qualifying the device response to his personal definition
> of what can be considered a color seems
> tyrannical.
You continue to post assumptions. It isn't my definition. It's Fairchild,
Giorgianni and Madden, GATF, Sharma and many others.
> The science is clearly agnostic to the concern of the meaning of qualia. The
> CIE model is an approximation.
Yes, what do you have that's better other than assuming?
> Andrew is free to pick what he feels is a useful distinction of color, but
> the system avoids this; a
> distinction is not required. In fact, the point of the system is to provide
> the tools to create whatever distinctions work for you.
I'm free to learn and then agree with actual experts in the field of color:
Fairchild, Giorgianni and Madden, GATF, Sharma and many others. You should
consider that idea.
> Then I began to notice something happening here to the dialog: the whole
> thing has become circular.
IOW, it's still unclear to you....
> Andrew issued an edict that any count of colors is only significant
> according to his personal CIE dE criteria which he is claiming as the
> philosophically one-true and real definition of color without questioning
> his methods or the limits of the CIE model and the fact that the CIE
> experiments were carried out using devices similar in physics to the ones
> he thinks over-count colors.
I've issued facts based on color science and agreed upon by many experts in the
field such as Fairchild, Giorgianni and Madden, GATF, Sharma and many others.
It's interesting you can't accept what they've written.
> Roger and Simon are replicating the color matching experiments that are the
> basis of the CIE model in terms of the model's measures of discernible
> differences and asking each other if you can apply these measures to create
> a discernible difference! And they're not sure, but suspect they can!
Well I've shown, using two software products I don't know if you own or know
how to use, that I can. That I am sure of!
> The web may explode at any moment.
Or your head.
> Andrew, I want to give you the benefit of my doubt for what seems a
> well-intentioned point of enlightenment about how to think about color in a
> way that's vigilant to gear-industry hyperbole. But your arguments read to
> me as mansplanation.
But don't doubt Fairchild, Giorgianni and Madden, GATF, Sharma and many experts
in this field others.
> I had wondered if Roger's original question was intended as a red herring?
More assumptions. They don't serve you well, please stop assuming.
> Now I see you're after teachable moments. But this makes for a rabbit hole.
It's not a rabbit hole. Some just can't accept colorimetric facts.
> (insert pithy Lewis Carrol Alice quote)
"If you don't know where you're going, any road will take you there." Lewis
Carroll
I don't believe you know where you're going based on your writings. Take any
road. ;-)
> I've nothing more to add, so over / out for now and carry on.
I believe you've made a wise choice.
Andrew Rodney
http://www.digitaldog.net/ <http://www.digitaldog.net/>
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