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: Wire ~ via colorsync-users <email@hidden>
- Date: Wed, 8 Jan 2020 06:50:47 -0800
Speaking for myself alone...
I can intellectually appreciate all these finer points.
And I enjoy the pedantic!
But there's an aspect of the burgeoning vernacular which becomes tedious
when it's a fight for control.
So as to parsing this stuff, pick the level and degree of detail
appropriate to the matter at hand, observe Occam's Razor, and goof around a
bit.
Under this preface, in context:
Cameras in the conventional sense of photographic technology didn't change
the world because they captured configurations of electromagnetic radiation
and exposed a plate which was chemically engraved to reveal the pattern of
rays passing from a scene through an aperture. No! Cameras affect us
because they produce images!
So vision is just such a basic and essential aspect of the topic of
imaging, and color is so essential to vision that if you are gonna tear
these apart it should be to make specific points about how the parts
interrelate, not to establish a divine covenant — or coven of witches, with
ritualistic rules and mantras — however academically well-informed your
practices may be.
Today a camera as most people possess one is a total colorimetric system.
And a whole lot more! A whole web connected PC has been put inside. It
emits fully colorimetrically formed images so reliably that even a phone
cam can be a reference standard. And it lets you assemble edit and
distribute anywhere with four-aces fidelity!
So what's going on with this desire to cast colorimetry out of it?
The only way this makes sense is if you think a camera is something other
than what — for example — I just described.
Maybe you think the camera ends at, idk, the sensor, or film plane? That's
well and good, but please be specific about what constitutes the device you
are describing so the context is clear.
If you say a camera has no gamut, I expect you to go on about the finer
points of fields, optics, sensors, signal processing, etc. If you just drop
it as bomb, I will wonder why are overcomplicating the matter?
This is where I find a touchy edge of desire for control. Because so much
of the economy is involved with persuading people to think the way a
person, or company, or industry needs them to think to keep their $
pipelines running.
And within the fight for business, there's the personal fight for status.
These factors make what otherwise be socratic discussions into turf wars.
I'm calling this out because it's in my nature to want to pursue the
socratic, but I see the imperatives and stresses of business at play.
It so happens I'm a total amateur and have nothing at stake but my
opinions, which I will happily change as I learn.
I realize others here have professional obligations and responsibilities
that make them more careful with their language.
On Tue, Jan 7, 2020 at 22:55 edmund ronald via colorsync-users <
email@hidden> wrote:
> 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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