Hello my colorful friends! I pray you are doing well. I have a math question for you. I would like to display the viewing conditions' illuminant and surround on a 1931 2deg chromaticity plot. These are un-normalized CIEXYZ values that need to be normalized within the plot range (0-1 both axes) first. Example: sRGB IEC 2.1 profile: Illuminant - 19.6445 20.3718 16.8089 Surround - 3.92889 4.07439 3.36179 How to normalize them? Please forgive my ignorance; I am learning every day. I thank you in advance for any support you might be able to provide. : ) Jeff Jeff Nova Chief Executive Officer Colorhythm https://colorhythm.com Mobile: +1 510-710-9590 Main: +1 415-399-9921
"normalizing to [0,1] first" does not make sense to me. When you calculate the (lower case) x,y for the chromaticity plot, the values are automatically between 0 and 1. x = (X)/(X+Y+Z) y = (Y)/(X+Y+Z)
On November 5, 2022 at 11:46 AM Jeff Nova via colorsync-users <colorsync-users@lists.apple.com> wrote:
Hello my colorful friends! I pray you are doing well.
I have a math question for you. I would like to display the viewing conditions' illuminant and surround on a 1931 2deg chromaticity plot. These are un-normalized CIEXYZ values that need to be normalized within the plot range (0-1 both axes) first.
Example:
sRGB IEC 2.1 profile:
Illuminant - 19.6445 20.3718 16.8089
Surround - 3.92889 4.07439 3.36179
How to normalize them? Please forgive my ignorance; I am learning every day.
I thank you in advance for any support you might be able to provide. : )
Jeff
Jeff Nova Chief Executive Officer
Colorhythm https://colorhythm.com Mobile: +1 510-710-9590 Main: +1 415-399-9921 _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/waynebretl%40cox.net
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Hi Wayne! Thank you for sharing your insight. I suppose I am trying to understand the ICC spec when it presents XYZ values “un-normalized” vs “normalized.” Putting aside the xy conversion … or is this what is meant? I’ll need to look at the spec again (and again and again…). Jeff
On Nov 5, 2022, at 12:42 PM, WAYNE BRETL <waynebretl@cox.net> wrote:
"normalizing to [0,1] first" does not make sense to me. When you calculate the (lower case) x,y for the chromaticity plot, the values are automatically between 0 and 1.
x = (X)/(X+Y+Z) y = (Y)/(X+Y+Z)
On November 5, 2022 at 11:46 AM Jeff Nova via colorsync-users <colorsync-users@lists.apple.com> wrote:
Hello my colorful friends! I pray you are doing well.
I have a math question for you. I would like to display the viewing conditions' illuminant and surround on a 1931 2deg chromaticity plot. These are un-normalized CIEXYZ values that need to be normalized within the plot range (0-1 both axes) first.
Example:
sRGB IEC 2.1 profile:
Illuminant - 19.6445 20.3718 16.8089
Surround - 3.92889 4.07439 3.36179
How to normalize them? Please forgive my ignorance; I am learning every day.
I thank you in advance for any support you might be able to provide. : )
Jeff
Jeff Nova Chief Executive Officer
Colorhythm https://colorhythm.com Mobile: +1 510-710-9590 Main: +1 415-399-9921 _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/waynebretl%40cox.net
This email sent to waynebretl@cox.net
-----Original Message----- From: waynebretl@cox.net <waynebretl@cox.net> Sent: Saturday, November 5, 2022 2:29 PM To: 'Jeff Nova' <jnova@colorhythm.com> Subject: RE: Normalizing CIEXYZ Values If you are trying to do a chromatic adaptation transform, I will let someone else answer, as I would probably get it wrong somewhere. Here's a Wikipedia intro: https://en.wikipedia.org/wiki/Chromatic_adaptation#CIE_color_appearance_mode... -----Original Message----- From: Jeff Nova <jnova@colorhythm.com> Sent: Saturday, November 5, 2022 2:18 PM To: WAYNE BRETL <waynebretl@cox.net> Cc: Jeff Nova via colorsync-users <colorsync-users@lists.apple.com> Subject: Re: Normalizing CIEXYZ Values Hi Wayne! Thank you for sharing your insight. I suppose I am trying to understand the ICC spec when it presents XYZ values “un-normalized” vs “normalized.” Putting aside the xy conversion … or is this what is meant? I’ll need to look at the spec again (and again and again…). Jeff
On Nov 5, 2022, at 12:42 PM, WAYNE BRETL <waynebretl@cox.net> wrote:
"normalizing to [0,1] first" does not make sense to me. When you calculate the (lower case) x,y for the chromaticity plot, the values are automatically between 0 and 1.
x = (X)/(X+Y+Z) y = (Y)/(X+Y+Z)
On November 5, 2022 at 11:46 AM Jeff Nova via colorsync-users <colorsync-users@lists.apple.com> wrote:
Hello my colorful friends! I pray you are doing well.
I have a math question for you. I would like to display the viewing conditions' illuminant and surround on a 1931 2deg chromaticity plot. These are un-normalized CIEXYZ values that need to be normalized within the plot range (0-1 both axes) first.
Example:
sRGB IEC 2.1 profile:
Illuminant - 19.6445 20.3718 16.8089
Surround - 3.92889 4.07439 3.36179
How to normalize them? Please forgive my ignorance; I am learning every day.
I thank you in advance for any support you might be able to provide. : )
Jeff
Jeff Nova Chief Executive Officer
Colorhythm https://colorhythm.com Mobile: +1 510-710-9590 Main: +1 415-399-9921 _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/waynebretl%40 cox.net
This email sent to waynebretl@cox.net
Regarding the larger question... Inside an ICC profile, for example, the PCS illuminant if XYZ is formatted as such: XYZ 0.9642 1 0.82491 while as I shared, the illuminant of viewing condition is like the example,19.6445 20.3718 16.8089 I would think that the first example has been normalized with the largest number = 1? - Jeff Jeff Nova Chief Executive Officer Colorhythm https://colorhythm.com Mobile: +1 510-710-9590 Main: +1 415-399-9921 On Sat, Nov 5, 2022 at 12:42 PM WAYNE BRETL <waynebretl@cox.net> wrote:
"normalizing to [0,1] first" does not make sense to me. When you calculate the (lower case) x,y for the chromaticity plot, the values are automatically between 0 and 1.
x = (X)/(X+Y+Z) y = (Y)/(X+Y+Z)
On November 5, 2022 at 11:46 AM Jeff Nova via colorsync-users < colorsync-users@lists.apple.com> wrote:
Hello my colorful friends! I pray you are doing well.
I have a math question for you. I would like to display the viewing conditions' illuminant and surround on a 1931 2deg chromaticity plot. These are un-normalized CIEXYZ values that need to be normalized within the plot range (0-1 both axes) first.
Example:
sRGB IEC 2.1 profile:
Illuminant - 19.6445 20.3718 16.8089
Surround - 3.92889 4.07439 3.36179
How to normalize them? Please forgive my ignorance; I am learning every day.
I thank you in advance for any support you might be able to provide. : )
Jeff
Jeff Nova Chief Executive Officer
Colorhythm https://colorhythm.com Mobile: +1 510-710-9590 Main: +1 415-399-9921 _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription:
https://lists.apple.com/mailman/options/colorsync-users/waynebretl%40cox.net
This email sent to waynebretl@cox.net
Jeff Nova via colorsync-users wrote:
I have a math question for you. I would like to display the viewing conditions' illuminant and surround on a 1931 2deg chromaticity plot. These are un-normalized CIEXYZ values that need to be normalized within the plot range (0-1 both axes) first.
Example:
sRGB IEC 2.1 profile:
Illuminant - 19.6445 20.3718 16.8089
Surround - 3.92889 4.07439 3.36179
How to normalize them? Please forgive my ignorance; I am learning every day.
Hello Jeff, when dealing with reflective or transmissive media, it is usual to relate measurements to 100% reflectance or transmittance of the light source. Typically the instrument does this for you - it measures the reflected/transmitted spectrum then divides by the actual instrument 100% illuminant spectrum, then computes the resultant XYZ by integrating over an (by ICC convention) D50 light source. That light source XYZ value will have a Y value of 1.0 or 100%, meaning that the measured values will also cover this range. Within the ICC profile itself reflectance or transmittance XYZ values have a nominal range of 0..1, although it is convention in other file formats (such as CGATS) to use a % range of 0..100. Some measurements might exceed 100% due to fluorescence etc. Viewing conditions will typically remain in absolute XYZ terms so as to convey the absolute light level, but if only the chromaticity is of interest, you could divide the XYZ by the Y value. As noted by Wayne Bretl, xy chromaticity values don't typically require this normalization since it is taken care of by the very nature of the calculation. Cheers, Graeme Gill.
participants (4)
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Graeme Gill
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Jeff Nova
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WAYNE BRETL
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