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 Author Topic: converting from prophoto to sRGB: tip  (Read 33966 times)
papa v2.0
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depends on your point of view (excuse the pun)! ho ho
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Jonathan Wienke
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To extend the argument to its logical confusion, papa v2.0 quoted "JBANES" when the correct author of the quote is actually "bjanes", therefore, nothing papa v2.0 says has any credibility whatsoever...
 « Last Edit: November 30, 2007, 12:20:04 AM by Jonathan Wienke » Logged

Eric Myrvaagnes
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To extend the argument to its logical confusion, papa v2.0 quoted "JBANES" when the correct author of the quote is actually "bjanes", therefore, nothing papa v2.0 says has any credibility whatsoever...
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That's what I call a "serious error".
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jjj
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You can apply such methods to determine what percentage of the population can perceive a particular wavelength of light, but you still have the problem of defining what the cutoff percentage is before defining whether a color is "visible" or not. That's where the arbitrariness comes in. Do you define something as "visible" when 10% of the test subjects can see it, 25%, 50%, or 90%?
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What if you applied the arbritary 10% cut off with regard to something more easily measurable such as human height, would that mean those at the 5% percentile at either end don't exist/aren't human?
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Ray
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What if you applied the arbritary 10% cut off with regard to something more easily measurable such as human height, would that mean those at the 5% percentile at either end don't exist/aren't human?
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Some of you guys sure like tying yourselves in knots  .

The question, 'is a particular color visible?' is very vague and therefore can only have a vague answer based on unstated assumptions. Make the question more precise by adding by whom, then you can get a more precise and meaningful answer.

'Is this color visible by 70% of the human population, by 10% of the human population, by 90% of a particular species of bird etc etc ?', then you can get a meaningful answer, if you do your research.

Part of the confusion is due to the colloqial and metaphorical way we use language where it is expected that the reader or listener will understand what we have missed out or not clearly defined. For example, the question itself, "Does the ProPhoto Color Space contain colors which cannot be seen by 'normal' humans?" implies that colors have an objective existence. But we know this is not true.

To avoid this untrue implication, perhaps the question should be something like, "Does the ProPhoto color space define the position of frequencies within the electromagnetic spectrum which cannot be seen by most humans?" One could then go on to make the question even more cumbersome by defining what is meant by 'seen".

Sometimes one just has to use a bit of common sense, ya know.
 « Last Edit: November 30, 2007, 09:57:45 PM by Ray » Logged
papa v2.0
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as we say in scotland

best you thats see a loon that canna swim

and see them drown
with oot the chance of  of oiffering your arm
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Ray
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as we say in scotland

best you thats see a loon that canna swim

and see them drown
with oot the chance of  of oiffering your arm
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No, papa! You cannot shed light on this by quoting gibberish.
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papa v2.0
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No, papa! You cannot shed light on this by quoting gibberish.
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Funny because what ive read here by the so called experts turns out to be quality gibberish.

including yourself!

"Does the ProPhoto color space define the position of frequencies within the electromagnetic spectrum which cannot be seen by most humans?"

need i say more
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digitaldog
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"Does the ProPhoto color space define the position of frequencies within the electromagnetic spectrum which cannot be seen by most humans?"
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Yes.
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Andrew Rodney
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Ray
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Yes.
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Thanks!
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Eric Myrvaagnes
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need i say more
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no.
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papa v2.0
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sorry guys

beep your expert on the last qoute

"Does the ProPhoto color space define the position of frequencies within the electromagnetic spectrum which cannot be seen by most humans?"

no it does not

come on guys you are letting the side down

lets go back to colour fundamentals

the pro photo or ROMM ' Primaries' only exist  in a manor  which has been evolved from the CIE COLORMETRY of CIEXYZ colour space

in order to define the human visual spectrum  we need to develop a primary that is not ' visible ' but a mathematical constraint for that colour space

hence the CIE XYZ space

the coordinates of these spaces include the colours we ca see and also  empty space as well!

there are no colors outside the human visual system!!!!!!!!

we are having a discussion on ProPhoto

so lets get there!
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eronald
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Hunt calls color a "percept". This elegant term does convey that a whole processing chain is involved in creating a percept, including not least an original active perception. Note also that practical color science is increasingly factoring the conditions under which the perception is taking place into mathematical description of the "color" perceived.

As a sidenote, I'd dispute that the eye is only a "sensor" for tristimulus information, if only because some women are quadrichromats  (and there are rods, and there is a substantial amount of compression and therefore processing going on, and and ...)

Edmund

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A further riposte to Papa:

If you want to nit-pick even further, color is a perception that occurs in the brain. The eye is only a sensor that transmits tri-stimulus color information to the brain, where it is processed, resulting in the perception of color. The eye may be working properly in a comatose person, but there will be no perception of color.

However, when presenting information to a general audience, some simplifications need to be made or else the presentation may be overwhelming. Thus, I am not considering the opponency theory of color, which would only muddle the issue further.

"Small minds are much distressed by little things. Great minds see them all but are not upset by them."

Francois de La Rochefoucauld
French author & moralist (1613 - 1680)
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 « Last Edit: December 04, 2007, 05:18:37 AM by eronald » Logged
bjanes
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As a sidenote, I'd dispute that the eye is only a "sensor" for tristimulus information, if only because some women are quadrichromats  (and there are rods, and there is a substantial amount of compression and therefore processing going on, and and ...)
Edmund
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Quick reference to the [a href=\"http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=303800]OMIM[/url] web site will show that human color vision is quite complex. A pertinent quote is, "...distinguished 2 types of normal color vision according to 'greenpoint,' i.e., the point at which the subject sees pure green, and 2 types according to 'bluepoint.' He presented the following genetic hypothesis: males can be of either G1/B1, G1/B2, or G2/B2; females can be of 6 genotypes."

From a brief reading of the description of the female tetrachromats, it would appear that rather than having an entirely new photo pigment, they merely may have two slightly different copies of the gene for the green pigment. One could debate is this is true tetrachromaticity.

Since the green gene is on the X-chromosome, us males can have only one copy of each gene, but there are differences among "normal" males in their green photo pigments, and all men may not see this color in quite the same way. Of course, color blind males see color quite differently. Some women could have more than 4 and up to 6 different photo pigments.

Any generalization concerning human psychology and physiology is likely to be a simplification, but many times a useful simplification for our comprehension of the processes. This leads to a veritable goldmine for nit-pickers .  However, current color theory is based on the tri-stimulus theory and the camera makers have not yet accommodated these female tetrachromats, and I do not think that these advances have been incorporated into the standard CIE observer database.

Hopefully, the authority of this reference will satisfy even Papa V2.0.
 « Last Edit: December 04, 2007, 08:00:05 AM by bjanes » Logged
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