RE: Humans (and cameras and scanners) do not have a color gamut (?)
The "Jack Holm" from HP? / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca@lists.apple.com> On Behalf Of Iliah Borg via colorsync-users Sent: Wednesday, January 8, 2020 4:36 PM To: Wayne Bretl <waynebretl@cox.net> Cc: 'Andrew Rodney via colorsync-users' <colorsync-users@lists.apple.com> Subject: Re: Humans (and cameras and scanners) do not have a color gamut (?)
See Jack Holm's paper ... where he derives the spectral locus of a combination of a sensor's outputs and a subsequent matrix
I've read that paper when it was first published on the web ;) It doesn't define sensor gamut, or gamut of sensor outputs. To quote, "This paper reports on the observed characteristics of the capture color analysis gamuts resulting from a number of capture devices/media, and scene analysis color matrices." The result depends on the matrix. Strongly depends, as the paper itself demonstrates. That matrix defines the relation between the camera observer and colorimetric observer. On Jan 8, 2020, at 4:21 PM, Wayne Bretl via colorsync-users wrote:
Arrgh - addressing problems - went only to iliah and not the whole list as intended
-----Original Message----- From: Wayne Bretl <waynebretl@cox.net> Sent: Wednesday, January 08, 2020 2:13 PM To: 'Iliah Borg' <iliah.i.borg@gmail.com> Subject: RE: Humans (and cameras and scanners) do not have a color gamut (?)
See Jack Holm's paper, which I posted above, where he derives the spectral locus of a combination of a sensor's outputs and a subsequent matrix: http://www.color.org/documents/CaptureColorAnalysisGamuts.pdf
Although he does not show the sensor outputs themselves, they have reached their extreme possible ratios when the stimulus is a single wavelength, and therefore a pseudo chromaticity chart could be plotted using the ratios of one channel to the sum of the three on one axis and a ratio of a second channel to the sum on the orthogonal axis. This chart would have a defined gamut of sensor values (inside the spectrum locus) but would not represent colors per se until processed through a matrix.
Holm shows the resulting chromaticities for multiple sensors and several reasonable matrices. He includes cases for motion picture negative film that clearly show a triangular gamut limit (spectral locus).
-----Original Message----- From: Iliah Borg <iliah.i.borg@gmail.com> Sent: Wednesday, January 08, 2020 1:59 PM To: Wayne Bretl <waynebretl@cox.net> Cc: Andrew Rodney <andrew@digitaldog.net>; Andrew Rodney via colorsync-users <colorsync-users@lists.apple.com> Subject: Re: Humans (and cameras and scanners) do not have a color gamut (?)
On Jan 8, 2020, at 3:52 PM, Wayne Bretl via colorsync-users wrote:
. The discussion has moved beyond the true but uninformative statement that cameras (sensors to be precise) do not have a color gamut , to considering how the gamut of sensor outputs
I would very much like a definition here. What is the gamut of sensor outputs?
And of course, how to measure it?
-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com
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This email sent to iliah.i.borg@gmail.com
-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com _______________________________________________ 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/graxx%40videotron.ca This email sent to graxx@videotron.ca
Yes, that's his name and company at the top of page 1. -----Original Message----- From: colorsync-users <colorsync-users-bounces+waynebretl=cox.net@lists.apple.com> On Behalf Of Roger Breton via colorsync-users Sent: Wednesday, January 08, 2020 2:51 PM To: colorsync-users@lists.apple.com Subject: RE: Humans (and cameras and scanners) do not have a color gamut (?) The "Jack Holm" from HP? / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca@lists.apple.com> On Behalf Of Iliah Borg via colorsync-users Sent: Wednesday, January 8, 2020 4:36 PM To: Wayne Bretl <waynebretl@cox.net> Cc: 'Andrew Rodney via colorsync-users' <colorsync-users@lists.apple.com> Subject: Re: Humans (and cameras and scanners) do not have a color gamut (?)
See Jack Holm's paper ... where he derives the spectral locus of a combination of a sensor's outputs and a subsequent matrix
I've read that paper when it was first published on the web ;) It doesn't define sensor gamut, or gamut of sensor outputs. To quote, "This paper reports on the observed characteristics of the capture color analysis gamuts resulting from a number of capture devices/media, and scene analysis color matrices." The result depends on the matrix. Strongly depends, as the paper itself demonstrates. That matrix defines the relation between the camera observer and colorimetric observer. On Jan 8, 2020, at 4:21 PM, Wayne Bretl via colorsync-users wrote:
Arrgh - addressing problems - went only to iliah and not the whole list as intended
-----Original Message----- From: Wayne Bretl <waynebretl@cox.net> Sent: Wednesday, January 08, 2020 2:13 PM To: 'Iliah Borg' <iliah.i.borg@gmail.com> Subject: RE: Humans (and cameras and scanners) do not have a color gamut (?)
See Jack Holm's paper, which I posted above, where he derives the spectral locus of a combination of a sensor's outputs and a subsequent matrix: http://www.color.org/documents/CaptureColorAnalysisGamuts.pdf
Although he does not show the sensor outputs themselves, they have reached their extreme possible ratios when the stimulus is a single wavelength, and therefore a pseudo chromaticity chart could be plotted using the ratios of one channel to the sum of the three on one axis and a ratio of a second channel to the sum on the orthogonal axis. This chart would have a defined gamut of sensor values (inside the spectrum locus) but would not represent colors per se until processed through a matrix.
Holm shows the resulting chromaticities for multiple sensors and several reasonable matrices. He includes cases for motion picture negative film that clearly show a triangular gamut limit (spectral locus).
-----Original Message----- From: Iliah Borg <iliah.i.borg@gmail.com> Sent: Wednesday, January 08, 2020 1:59 PM To: Wayne Bretl <waynebretl@cox.net> Cc: Andrew Rodney <andrew@digitaldog.net>; Andrew Rodney via colorsync-users <colorsync-users@lists.apple.com> Subject: Re: Humans (and cameras and scanners) do not have a color gamut (?)
On Jan 8, 2020, at 3:52 PM, Wayne Bretl via colorsync-users wrote:
. The discussion has moved beyond the true but uninformative statement that cameras (sensors to be precise) do not have a color gamut , to considering how the gamut of sensor outputs
I would very much like a definition here. What is the gamut of sensor outputs?
And of course, how to measure it?
-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com
_______________________________________________ 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/iliah.i.borg%4 0gmail.com
This email sent to iliah.i.borg@gmail.com
-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com _______________________________________________ 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/graxx%40videotron.ca This email sent to graxx@videotron.ca _______________________________________________ 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
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Wayne Bretl