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Author Topic: Bit-Depth understanding required  (Read 18152 times)
Ray
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« Reply #40 on: July 26, 2006, 07:37:18 AM »
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It turns out that birds have a fourth sensor between the blue and green and have better and more extended color vision than humans.


Bill,
Very interesting stuff. Yes, I've read of this fourth primary color sense which some birds are supposed to have. It explains to some extent the brilliant blue plumage that some 'birds of paradise' display.

What struck me as interesting in the photo.net article you refer to is the 'red' receptor or cone is most sensitive to yellow, not red, that is, light with a wavelength of 580 nm, hence the argument in favour of yellow fire engines.
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PeterLange
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« Reply #41 on: July 26, 2006, 03:19:08 PM »
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To make it clearer for those who might be confused by tables....

In addition to Bill’s and Oscar’s posts,
let me try to develop an example:

… by first creating a most saturated Yellow in CIE RGB:
RGB = 255, 255, 0
HSB = 60, 100, 100

… now, referring to the CIE color matching functions
(see page 4: http://www.fho-emden.de/~hoffmann/ciexyz29082000.pdf)
it can be easily seen that the r and g weighting curves meet each other at about 570 nm.

… so IF my humble monitor would be able to show all CIE RGB colors
based on the respective RGB primaries of 700/546.1/435.8 nm
(in the sense of a thought experiment)
above created yellow would look right the same
as a spectrally pure yellow of 570 nm.

At least this should be valid for the standard human observer; neither for birds nor for people with fancy perception.

Peter

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Dennis
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« Reply #42 on: July 27, 2006, 07:27:53 AM »
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It turns out that birds have a fourth sensor between the blue and green and have better and more extended color vision than humans.
It's not a trick, it's a SONY ;-)

 I always thought, that SONY invented the RGBE pattern...
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Dennis.
Dennis
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« Reply #43 on: July 27, 2006, 07:42:48 AM »
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All colors of light are composed of the three primary colors for light, Red, Green and Blue.
Aha. Would you say, that the yellow light of the sodium emission spectrum is composed by red and green?


(http://library.thinkquest.org/21008/data/sky/spectroscopy1.htm)

All colors of light can be composed of the three primary colors for light
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Dennis.
Ray
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« Reply #44 on: July 27, 2006, 07:14:39 PM »
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All colors of light can be composed of the three primary colors for light
[a href=\"index.php?act=findpost&pid=71849\"][{POST_SNAPBACK}][/a]


I agree, this distinction should be made and it appears is sometimes forgotten by many of us, including me. I now wonder what the difference would be between a red and green light, superimposed, neither of which extended into the yellow part of the spectrum, and a red and green light which both extended into the yellow region. I presume one would experience a sensation of 'brighter' yellow, but maybe not.
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DiaAzul
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« Reply #45 on: July 28, 2006, 03:11:24 AM »
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All colors of light are composed of the three primary colors for light, Red, Green and Blue.

I agree, this distinction should be made and it appears is sometimes forgotten by many of us, including me. I now wonder what the difference would be between a red and green light, superimposed, neither of which extended into the yellow part of the spectrum, and a red and green light which both extended into the yellow region. I presume one would experience a sensation of 'brighter' yellow, but maybe not.
[a href=\"index.php?act=findpost&pid=71914\"][{POST_SNAPBACK}][/a]

Jack's original comment needs some modification - OUR PERCEPTION / VISUAL SYSTEM can be fooled into seeing all colours by careful stimulation of the rods and cones by the three primary colours. The three primary colours being those colours to which the rods/cones each individually are most sensitive.

It is not possible in physics to create a new colour (wavelength) by mixing three separate colours (wavelength) in the way that is being conveyed in this thread.


The choice of three primary colours is arbitrary in any system and, ideally, the camera sensor, display and printer primary colours (and colour response charactersitics) should match those of the average human eye (forget the need for the argument over sRGB, aRGB, ProPhoto, etc..which gives the best match to our own visual system).
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David Plummer    http://photo.tanzo.org/
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« Reply #46 on: July 28, 2006, 05:00:16 AM »
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Jack's original comment needs some modification - OUR PERCEPTION / VISUAL SYSTEM can be fooled into seeing all colours by careful stimulation of the rods and cones by the three primary colours. The three primary colours being those colours to which the rods/cones each individually are most sensitive.

It is not possible in physics to create a new colour (wavelength) by mixing three separate colours (wavelength) in the way that is being conveyed in this thread.
The choice of three primary colours is arbitrary in any system and, ideally, the camera sensor, display and printer primary colours (and colour response charactersitics) should match those of the average human eye (forget the need for the argument over sRGB, aRGB, ProPhoto, etc..which gives the best match to our own visual system).
[a href=\"index.php?act=findpost&pid=71973\"][{POST_SNAPBACK}][/a]


Nope, forget all of this...

It turns out that, in order to simulate ALL visible colors with a single set of primaries, these primaries have to be defined outside the visible spectrum.

So ALL colors of light are NOT composed of some combination of a single set of REAL primaries, and that sort of eliminates the possibility of an ideal device with human response characteristics.

Think of the colorful shoe-sole. Can we define three points within this set that completely encompass the entire set?
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Oscar Rysdyk
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DiaAzul
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« Reply #47 on: July 28, 2006, 12:24:08 PM »
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So ALL colors of light are NOT composed of some combination of a single set of REAL primaries, and that sort of eliminates the possibility of an ideal device with human response characteristics.

[a href=\"index.php?act=findpost&pid=71984\"][{POST_SNAPBACK}][/a]

But we don't need to talk about all colours of light...only those that we can actually see. What is the point of recording colours that will be neither reproducable nor observable? That type of device may be required in a scientific or engineering environment, but for photography leading to viewable images there is no need to go to the obsessive extremes of the perfect device at exhorbitant cost.
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David Plummer    http://photo.tanzo.org/
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« Reply #48 on: July 29, 2006, 05:39:13 AM »
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But we don't need to talk about all colours of light...only those that we can actually see. What is the point of recording colours that will be neither reproducable nor observable? That type of device may be required in a scientific or engineering environment, but for photography leading to viewable images there is no need to go to the obsessive extremes of the perfect device at exhorbitant cost.
 

So you're suggesting that IR and UV photography "isn't necessary", or that photography is always documentary of 'that we can actually see"?

I also suggest you read up a bit on human vision; the response curves cited around here are the normalised curves based on tests on a selection of humans. It most certainly isn't how everybody see.

Try looking up e.g. tetrachromacy, or at the very least read the basic articles about human color vision and color blindness on Wikipedia.
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Jan
PeterLange
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« Reply #49 on: July 29, 2006, 04:49:43 PM »
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But we don't need to talk about all colours of light...only those that we can actually see. What is the point of recording colours that will be neither reproducable nor observable? That type of device may be required in a scientific or engineering environment, but for photography leading to viewable images there is no need to go to the obsessive extremes of the perfect device at exhorbitant cost.
[a href=\"index.php?act=findpost&pid=72012\"][{POST_SNAPBACK}][/a]
Imaginary colors & primaries are just a tradeoff to hold more or even all colors of human vision within a ‘triangular’ matrix space.

Monitors are of course limited to real-world phosphors / primaries.
Cameras are not.

Peter

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DiaAzul
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« Reply #50 on: July 30, 2006, 02:03:44 PM »
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So you're suggesting that IR and UV photography "isn't necessary", or that photography is always documentary of 'that we can actually see"?

I also suggest you read up a bit on human vision; the response curves cited around here are the normalised curves based on tests on a selection of humans. It most certainly isn't how everybody see.

Try looking up e.g. tetrachromacy, or at the very least read the basic articles about human color vision and color blindness on Wikipedia.
[a href=\"index.php?act=findpost&pid=72054\"][{POST_SNAPBACK}][/a]

So what is your point, other than trying to be patronising?
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David Plummer    http://photo.tanzo.org/
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« Reply #51 on: July 30, 2006, 06:20:35 PM »
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So what is your point, other than trying to be patronising?
My point was not about trying to be patronising at all.

I was just shocked at your attitude towards IR and UV photography, that you should think that it somehow isn't usable for other than "scientific or engineering", and that you seemed so ignorant of the variations in human vision.

While a device doesn't need to be "perfect" -- whatever you mean by that -- there certainly are other uses -- artistic uses, like those of e.g. Bjørn Rørslett or our patron's -- than those represented with a very basic trichromatic model centered around narrowly chosen primaries.
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Jan
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