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Dale 12-12-2012 08:15 AM

color wheel
 
My Uncle is an artist

I have ten years work experience as an imaging system engineer

I was always under the impression that CMY were the color complements or
opposites of RGB

he and apparently many others use a color wheel where the are other
complements or opposites to RGB

does anyone know why this situation is? are there two rights or is
someone wrong?


--
Dale

Tim Conway 12-12-2012 09:31 AM

Re: color wheel
 

"Dale" <invalid@invalid.invalid> wrote in message
news:66640c.rc7.19.1@news.alt.net...
> My Uncle is an artist
>
> I have ten years work experience as an imaging system engineer
>
> I was always under the impression that CMY were the color complements or
> opposites of RGB
>
> he and apparently many others use a color wheel where the are other
> complements or opposites to RGB
>
> does anyone know why this situation is? are there two rights or is someone
> wrong?
>
>

There are others here that can answer you better. As far as I know it is
"two rights". RGB is generally in tv, video, photography etc. CMY(K) is
usually used in the printing industry. An example is the computer/monitor
is RGB, whereas your printer goes by CMYK. Both arrive at the same image
though or try to.
Tim



Me 12-12-2012 10:50 AM

Re: color wheel
 
On 12/12/2012 10:31 p.m., Tim Conway wrote:
> "Dale" <invalid@invalid.invalid> wrote in message
> news:66640c.rc7.19.1@news.alt.net...
>> My Uncle is an artist
>>
>> I have ten years work experience as an imaging system engineer
>>
>> I was always under the impression that CMY were the color complements or
>> opposites of RGB
>>
>> he and apparently many others use a color wheel where the are other
>> complements or opposites to RGB
>>
>> does anyone know why this situation is? are there two rights or is someone
>> wrong?
>>
>>

> There are others here that can answer you better. As far as I know it is
> "two rights". RGB is generally in tv, video, photography etc. CMY(K) is
> usually used in the printing industry. An example is the computer/monitor
> is RGB, whereas your printer goes by CMYK. Both arrive at the same image
> though or try to.
> Tim
>
>

Google "additive and subtractive colour".
Easy to visualise if you understand that 50:50 red and green pixels on a
monitor give you bright yellow, red and green paint (or ink) mixed 50:50
give you a dirty brown, even if dirty brown is just "dark yellow".


ray 12-12-2012 04:40 PM

Re: color wheel
 
On Wed, 12 Dec 2012 03:15:14 -0500, Dale wrote:

> My Uncle is an artist
>
> I have ten years work experience as an imaging system engineer
>
> I was always under the impression that CMY were the color complements or
> opposites of RGB
>
> he and apparently many others use a color wheel where the are other
> complements or opposites to RGB
>
> does anyone know why this situation is? are there two rights or is
> someone wrong?


http://en.wikipedia.org/wiki/Complementary_colors

indicates that it depends on what your primary colors are - the
complement of a color is obtained by mixing equal portions of the other
two primaries.

Thomas Richter 12-12-2012 05:47 PM

Re: color wheel
 
On 12.12.2012 09:15, Dale wrote:
> My Uncle is an artist
>
> I have ten years work experience as an imaging system engineer
>
> I was always under the impression that CMY were the color complements or
> opposites of RGB
>
> he and apparently many others use a color wheel where the are other
> complements or opposites to RGB
>
> does anyone know why this situation is? are there two rights or is
> someone wrong?


All wrong. First of all, RGB is not a color system. There isn't "one
RGB", there is at best a color gamut, and RGB are three primaries picked
arbitrary within the gamut. However, that's a subset of all available
colors, namely everything within the RGB triangle. A popular choice for
primaries are of course red, green and blue, but do not need to be. Any
three linearly independent colors do.

Thus, *a* RGB color space (not *the*...) is the triangle in the XYZ
color gamut spawned by three primaries. These may or may not be red,
green and blue.

Second, CMY (or CMYK) is often referred to as "subtractive" color
format, though this is highly misleading. I would rather call this a
multiplicative color space. In RGB, the output color is generated by
additive mixture (overlay) of colors. In CMY, a white color input
undergoes filtering by three spectral filters. Thus, a C (cyan) filter
would remove red. This is multiplicative because the filter
characteristic of applying two filters (such as C and M) is a filter
whose spectral sensitivity is the pointwise product of the C and M filter.

As for RGB, which primaries you pick is entirely up to you. There is no
need for them to be C, M and Y, though this a popular choice. CMY models
the color reproduction in print - color pigments act as filters, RGB the
color reproduction of displays, where light mixes.


Martin Leese 12-12-2012 06:21 PM

Re: color wheel
 
Dale wrote:
> My Uncle is an artist
>
> I have ten years work experience as an imaging system engineer
>
> I was always under the impression that CMY were the color complements or
> opposites of RGB
>
> he and apparently many others use a color wheel where the are other
> complements or opposites to RGB


What are these "other complements or
opposites to RGB"? I have a friend who is a
photographer. He was taught, and always
refers to, Blue, Red, Yellow filters on his
colour enlarger but, when I looked, these
were simply unusual names for Cyan, Magenta,
Yellow.

> does anyone know why this situation is? are there two rights or is
> someone wrong?


What you describe is really two *wrongs*, as
human perception uses something close to Lab.

--
Regards,
Martin Leese
E-mail: please@see.Web.for.e-mail.INVALID
Web: http://members.tripod.com/martin_leese/

Paul Ciszek 12-12-2012 11:45 PM

Re: color wheel
 

In article <66640c.rc7.19.1@news.alt.net>,
Dale <invalid@invalid.invalid> wrote:
>My Uncle is an artist
>
>I have ten years work experience as an imaging system engineer
>
>I was always under the impression that CMY were the color complements or
>opposites of RGB


In printing, that is definately true--cyan is the absence of red, magenta
is the absence of green, and yellow is the absence of blue.

>he and apparently many others use a color wheel where the are other
>complements or opposites to RGB


http://en.wikipedia.org/wiki/RYB_color_model

Artists tend to think of red, yellow and blue as the primary colors.
And, for some reason, this system works when you are mixing paints.
Red and yellow give you orange, yellow and blue give you green, and
red and blue give you purple. Three primaries + three secondaries
give you six basic colors, seen on the pride flag, most non-technical
color wheels, and cartoon depictions of rainbows. Personally, I find
the artist's color wheel with red, yellow and blue equally spaced more
aesthetically pleasing than the RGB color wheel. Anyway, on the artist's
color wheel, the complimentary pairs are red-green, yellow-purple, and
blue-orange.

>does anyone know why this situation is? are there two rights or is
>someone wrong?


Artists came up with this color system long before the physics of color
vision were understood, so it is not surprising that they identified
a different set of primaries. I wouldn't call it "wrong", either. To
me, green "looks like" a mixture of blue and yellow, while yellow does
*not* "look like" a mixture of red and green. Of course, this could be
a cultural bias implanted back in pre-school, I don't know.

--
"Remember when teachers, public employees, Planned Parenthood, NPR and PBS
crashed the stock market, wiped out half of our 401Ks, took trillions in
TARP money, spilled oil in the Gulf of Mexico, gave themselves billions in
bonuses, and paid no taxes? Yeah, me neither."


Dale 12-13-2012 01:52 AM

Re: color wheel
 
On 12/12/2012 12:47 PM, Thomas Richter wrote:
> On 12.12.2012 09:15, Dale wrote:
>> My Uncle is an artist
>>
>> I have ten years work experience as an imaging system engineer
>>
>> I was always under the impression that CMY were the color complements or
>> opposites of RGB
>>
>> he and apparently many others use a color wheel where the are other
>> complements or opposites to RGB
>>
>> does anyone know why this situation is? are there two rights or is
>> someone wrong?

>
> All wrong. First of all, RGB is not a color system. There isn't "one
> RGB", there is at best a color gamut, and RGB are three primaries picked
> arbitrary within the gamut. However, that's a subset of all available
> colors, namely everything within the RGB triangle. A popular choice for
> primaries are of course red, green and blue, but do not need to be. Any
> three linearly independent colors do.
>
> Thus, *a* RGB color space (not *the*...) is the triangle in the XYZ
> color gamut spawned by three primaries. These may or may not be red,
> green and blue.
>
> Second, CMY (or CMYK) is often referred to as "subtractive" color
> format, though this is highly misleading. I would rather call this a
> multiplicative color space. In RGB, the output color is generated by
> additive mixture (overlay) of colors. In CMY, a white color input
> undergoes filtering by three spectral filters. Thus, a C (cyan) filter
> would remove red. This is multiplicative because the filter
> characteristic of applying two filters (such as C and M) is a filter
> whose spectral sensitivity is the pointwise product of the C and M filter.
>
> As for RGB, which primaries you pick is entirely up to you. There is no
> need for them to be C, M and Y, though this a popular choice. CMY models
> the color reproduction in print - color pigments act as filters, RGB the
> color reproduction of displays, where light mixes.
>


yeah I forget, there is no one RGB or CMY

--
Dale

Dale 12-13-2012 01:53 AM

Re: color wheel
 
On 12/12/2012 06:45 PM, Paul Ciszek wrote:
> In article <66640c.rc7.19.1@news.alt.net>,
> Dale <invalid@invalid.invalid> wrote:
>> My Uncle is an artist
>>
>> I have ten years work experience as an imaging system engineer
>>
>> I was always under the impression that CMY were the color complements or
>> opposites of RGB

>
> In printing, that is definately true--cyan is the absence of red, magenta
> is the absence of green, and yellow is the absence of blue.
>
>> he and apparently many others use a color wheel where the are other
>> complements or opposites to RGB

>
> http://en.wikipedia.org/wiki/RYB_color_model
>
> Artists tend to think of red, yellow and blue as the primary colors.
> And, for some reason, this system works when you are mixing paints.
> Red and yellow give you orange, yellow and blue give you green, and
> red and blue give you purple. Three primaries + three secondaries
> give you six basic colors, seen on the pride flag, most non-technical
> color wheels, and cartoon depictions of rainbows. Personally, I find
> the artist's color wheel with red, yellow and blue equally spaced more
> aesthetically pleasing than the RGB color wheel. Anyway, on the artist's
> color wheel, the complimentary pairs are red-green, yellow-purple, and
> blue-orange.
>
>> does anyone know why this situation is? are there two rights or is
>> someone wrong?

>
> Artists came up with this color system long before the physics of color
> vision were understood, so it is not surprising that they identified
> a different set of primaries. I wouldn't call it "wrong", either. To
> me, green "looks like" a mixture of blue and yellow, while yellow does
> *not* "look like" a mixture of red and green. Of course, this could be
> a cultural bias implanted back in pre-school, I don't know.
>


thanks

--
Dale

Dale 12-13-2012 01:55 AM

Re: color wheel
 
On 12/12/2012 01:21 PM, Martin Leese wrote:
> Dale wrote:
>> My Uncle is an artist
>>
>> I have ten years work experience as an imaging system engineer
>>
>> I was always under the impression that CMY were the color complements
>> or opposites of RGB
>>
>> he and apparently many others use a color wheel where the are other
>> complements or opposites to RGB

>
> What are these "other complements or
> opposites to RGB"? I have a friend who is a
> photographer. He was taught, and always
> refers to, Blue, Red, Yellow filters on his
> colour enlarger but, when I looked, these
> were simply unusual names for Cyan, Magenta,
> Yellow.


he uses a standard artist's color wheel, yu can find on the net

>
>> does anyone know why this situation is? are there two rights or is
>> someone wrong?

>
> What you describe is really two *wrongs*, as
> human perception uses something close to Lab.
>


yeah, I know Lab or Luv is more definitive

--
Dale


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