attention color whizes: non-typical sRGB/RGB/ProPhoto question

[Graystar]

So, what is the value for white point in XYZ again?

Who cares.  That's not how it's officially specified.

[Iliah]

Who cares.  That's not how it's officially specified.

 

[Peter_DL]

Now does the record of colour in a raw file follow cone response?

Of course it is meant to do that.
Doubts ?
 
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[Iliah]

Of course it is meant to do that.
Doubts ?
 
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No doubts. If what you are seem to suggest be true we would not encounter any problems with different colour transforms for different cameras.

[Graystar]

Well, if you want to be a stickler for the rules then it's [1,1,1] but it's XYZ, not XYZ.

[Iliah]

Well, if you want to be a stickler for the rules then it's [1,1,1] but it's XYZ, not XYZ.

From your very first post it was all obvious. You do not know what you are talking about.

[Peter_DL]

No doubts. If what you are seem to suggest be true we would not encounter any problems with different colour transforms for different cameras.

No one said it's perfect.

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[Iliah]

No one said it's perfect.

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It is not about being perfect. The responses do not follow LMS intentionally, by design, in order to get better noise characteristics (one of the reasons).

[Peter_DL]

It is not about being perfect. The responses do not follow LMS intentionally, by design, in order to get better noise characteristics (one of the reasons).

Ever studied the design of Bayer filters ?

Actually, to create a camera filter set that is "perfect", it is not required to exactly the match the human cone responses (or the XYZ responses). All that is required is the filter responses be some linear combination of the human cone responses. If that is the case, then a simple 3 by 3 matrix can be used in software to recover the exact XYZ values.

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[Graystar]

From your very first post it was all obvious. You do not know what you are talking about.

XYZ refers to the color matching functions.

XYZ refers to the tristimulus values.

The button text in the calculator refer to names of the color spaces.

Joofa simply called his [1,1,1] values XYZ, leaving the question open as it being xyz or XYZ.

CIE XYZ white is specified in xyz.

And no matter how you (properly) slice it, Adobe RGB is fully contained within Pro Photo.  Anyone who thinks it isn't is the one who doesn't know what he's talking about.

[joofa]

Joofa simply called his [1,1,1] values XYZ, leaving the question open as it being xyz or XYZ.

The sum of xyz [1/3,1/3,1/3] should be one (1/3+1/3+1/3=1). So if I wrote [1,1,1] then it should be obvious what the intention was. And, [1/3,1/3,1/3] and [1,1,1] are the same "color", only the magnitude is different.

Joofa

[tho_mas]

According to "Joofa" ProPhoto doesn't encompass all the colours AdobeRGB contains.
Maybe "Joofa" can also explain why I can create gradients in ProPhoto going from pure cyan to white & pure cyan to pure blue & pure blue to white that totally* clip when I convert relcol to AdobeRGB?
If AdobeRGB would exceed ProPhoto in blues/cyans some (saturated) colours should not show clipping. But they do. How so?

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* some light, low saturated blues and cyans do not clip, of course, but all high saturated colours do show clipping

[Iliah]

> Ever studied the design of Bayer filters ?

Collected spectral data on the response of most of popular cameras.

> Actually, to create a camera filter set that is "perfect", it is not required to exactly the match the human cone responses (or the XYZ responses). All that is required is the filter responses be some linear combination of the human cone responses. If that is the case, then a simple 3 by 3 matrix can be used in software to recover the exact XYZ values.

Yes, more or less. But as I said - it contradicts other design goals; so Luther-Ives condition is not followed too closely, to put it mildly.

[joofa]

Also Joofa: Hilbert Space? Seriously? Why stop there? If you really want to set up a smoke screen, you should invoke Zariski–Riemann space.

Mark, you might have noticed that I was stressing a lot on a single color space with multiple coordinate systems. In order to represent seemingly different color spaces that I showed in my plot I had to follow some tricks. In my representation the colorimeteric XYZ data was not plotted.

Hope that helps.

Sincerely,

Joofa

[Iliah]

You are not qualified to judge as you do not know the basics. In the very same posting where you were putting down Joofa's contribution you made a first grade mistake probably only to prove your own thesis that not all contributions are equally useful. You lost it 

[joofa]

According to "Joofa" ProPhoto doesn't encompass all the colours AdobeRGB contains.
Maybe "Joofa" can also explain why I can create gradients in ProPhoto going from pure cyan to white & pure cyan to pure blue & pure blue to white that totally* clip when I convert relcol to AdobeRGB?
If AdobeRGB would exceed ProPhoto in blues/cyans some (saturated) colours should not show clipping. But they do. How so?

___________________
* some light, low saturated blues and cyans do not clip, of course, but all high saturated colours do show clipping

When did I say cyans? I primarily concentrated in an area around saturated blues in Adobe RGB (D65). And, it turned out that a strip from that area to white was also problematic. As far as cyans are concerned, if you can ball park them in my plot you might see what is happening:

Sincerely,

Joofa

[Peter_DL]

Yes, more or less. But as I said - it contradicts other design goals; so Luther-Ives condition is not followed too closely, to put it mildly.

Mildly interesting.
So why did you ask at all in post # 373 (?).

Note that this is not dpreview, it is not about having to have right
(without intending to express any disrespect for those who contribute at dpreview).

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[Graystar]

You are not qualified to judge as you do not know the basics. In the very same posting where you were putting down Joofa's contribution you made a first grade mistake probably only to prove your own thesis that not all contributions are equally useful. You lost it 

I made no mistake...only from your point of view.  You're just upset because you made the same mistake that Joofa did with the Bruce Lindbloom calculator...thinking that the "Ref White" changes the white point of the selected RGB space, when it fact it does not such thing.  Your position is based on incorrect conversions.

[Iliah]

> I made no mistake

 

[Iliah]

> So why did you ask at all in post # 373 (?).

Because I wanted to know the basis of your statement.