Re: Humans (and cameras and scanners) do not have a color gamut (?)
Re: Humans (and cameras and scanners) do not have a color gamut (?)
- Subject: Re: Humans (and cameras and scanners) do not have a color gamut (?)
- From: edmund ronald via colorsync-users <email@hidden>
- Date: Wed, 8 Jan 2020 07:54:55 +0100
I don’t see what a camera really has to do with color; the word
colorimetric doesn’t really come into it except rather late because
colorimetry starts out as a way of making more precise the psychophysics of
color perception. As a camera can does not create a color impression per
se, we would have to create a whole capture and rendering environment
before we can talk about colorimetry related to that camera, even if we
assume a “standard observer” - such observer being themselves a fiction
created by the priests of ... colorimetry.
Disclaimer, my knowledge of the topic only comes from talking Dr. Hunt’s
introductory course, and of course I am just an amateur scientist, and not
as smart as Iliah or Andrew.
Edmund
On Tue, Jan 7, 2020 at 11:35 PM Iliah Borg via colorsync-users <
email@hidden> wrote:
>
> On Jan 7, 2020, at 5:12 PM, Henry Davis via colorsync-users wrote:
>
> > This part is still confusing:
> >> The closer the transform from camera observer to human observer is to
> one-to-one, the easier it is to speak of “colour accuracy”.
> > It just seems that there has to be limitations within the response of
> the camera.
>
> Yes, measurement range and measurement accuracy impose limitations.
> Convolution of spectrum to 3-channel data numbers impose limitations.
> Measurement accuracy and ambiguity of convolution varies with the source
> colour (the colour presented to a camera).
>
> > So, don’t call it a gamut - but if there is some limitation what would
> it be called.
>
> Accuracy.
>
> > Is the camera able to respond to the entirety of the visual spectrum
>
> Like an exposure meter, or, better, light meter, camera responds to any
> light visible to a human (and wider, some UV, some IR that still passes hot
> mirror and is shorter than 1200)
>
> > accurately, one-to-one?
>
> No. Metameric error is always present, convolution results in error, plus
> there is the question of measurement accuracy.
>
> > I get how there is not a one-to-one transform from camera to the human
> observer.
> >
> > The transform that takes place from world to camera is made with
> numbers. If those numbers are exactly the same numbers that are used to
> define/describe the visible spectrum then I think I can better understand
> the discussion.
>
> A camera is a colormeter, and colormeter readings are just 3 numbers.
> Suppose they are XYZ. Restoring spectrum from XYZ data alone is impossible,
> because XYZ represent a convolution of spectrum (based on an observer).
> During this convolution a lot of original data is lost.
>
>
> --
> Best regards,
> Iliah Borg
> LibRaw, LLC
> www.libraw.org
> www.rawdigger.com
> www.fastrawviewer.com
>
>
>
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