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: Iliah Borg via colorsync-users <email@hidden>
- Date: Tue, 7 Jan 2020 17:35:07 -0500
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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