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 08:13:49 +0100
The word I mistyped was “sense-impressions”
On Wed, Jan 8, 2020 at 8:13 AM edmund ronald <email@hidden> wrote:
> BTW I think this type of discussion is quite helpful because it exposes
> all sorts of computer geeks and photographers who lurk here to the idea
> that what they are doing is twiddling the buttons on some very cumbersome
> tech that is quite distant from what humans perceive. This can be demoed
> easily when one takes a multispectral capture, and suddenly realises that
> although a lot of information has been stored it is hard to transform this
> back into valid dense-impressions.
>
> Edmund
>
> On Wed, Jan 8, 2020 at 7:54 AM edmund ronald <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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