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From: Jacob Rus on 8 Mar 2010 18:42
Incidentally, in case anyone wants a "proper Granger rainbow" (which
is to say, the edge of an HSL cylinder) of their own, without
following the steps above, I've uploaded one here:
http://www.mediafire.com/?2mmam2mdyzt

Just resize this photoshop file to any desired dimensions.

Cheers,
Jacob
From: Mike Russell on 9 Mar 2010 01:25
On Mon, 8 Mar 2010 15:42:18 -0800 (PST), Jacob Rus wrote:

> Incidentally, in case anyone wants a "proper Granger rainbow" (which
> is to say, the edge of an HSL cylinder) of their own, without
> following the steps above, I've uploaded one here:
> http://www.mediafire.com/?2mmam2mdyzt
>
> Just resize this photoshop file to any desired dimensions.
>
> Cheers,
> Jacob

May not be useful, but it sure looks pretty. Reminds me of the rainbow I
saw on the way back from work today.

Interesting that there are relatively bright vertical lines at the CMY
hues, but not at the RGB ones. I'll venture a guess that this is because
these hues have two sets of pixels contributing photons, instead of only
one.

So, for example RGB(255,0,0) will be less bright than RGB(255,255,0) or
RGB(255,0,255).
--
Mike Russell - http://www.curvemeister.com
From: Jacob Rus on 10 Mar 2010 05:23
Mike Russell wrote:
> Interesting that there are relatively bright vertical lines at the CMY
> hues, but not at the RGB ones.  I'll venture a guess that this is because
> these hues have two sets of pixels contributing photons, instead of only
> one.  
>
> So, for example RGB(255,0,0) will be less bright than RGB(255,255,0) or
> RGB(255,0,255).

Pretty much. If you look at the deformations that go into making the
HSL cylinder from an RGB cube – in the diagram <http://
en.wikipedia.org/wiki/File:Hsl-and-hsv.svg> look at the tilted cube in
the top middle and notice that the following step pushes red, green,
and blue *up*, while pushing cyan, yellow, and magenta *down* – these
bright vertical lines are the top three edges of the cube (stretching
between white and C, M, or Y). At red, green, and blue, there are also
vertical lines, but they're darker than the surrounding area, rather
than lighter.

Cheers,
Jacob
From: Mike Russell on 10 Mar 2010 05:46
On Wed, 10 Mar 2010 02:23:48 -0800 (PST), Jacob Rus wrote:

> Mike Russell wrote:
>> Interesting that there are relatively bright vertical lines at the CMY
>> hues, but not at the RGB ones.  I'll venture a guess that this is because
>> these hues have two sets of pixels contributing photons, instead of only
>> one.  
>>
>> So, for example RGB(255,0,0) will be less bright than RGB(255,255,0) or
>> RGB(255,0,255).
>
> Pretty much. If you look at the deformations that go into making the
> HSL cylinder from an RGB cube – in the diagram <http://
> en.wikipedia.org/wiki/File:Hsl-and-hsv.svg> look at the tilted cube in
> the top middle and notice that the following step pushes red, green,
> and blue *up*, while pushing cyan, yellow, and magenta *down* – these
> bright vertical lines are the top three edges of the cube (stretching
> between white and C, M, or Y). At red, green, and blue, there are also
> vertical lines, but they're darker than the surrounding area, rather
> than lighter.
>
> Cheers,
> Jacob

Ah - hadn't quite pieced that together. Thanks. This also explains the
varying width of the colored bands for RGB and CMY on the default "rainbow"
gradient, and the rainbow pattern on the color picker hue slider.

BTW - I just noticed that there is a mini-Granger chart along the bottom of
the color palette. I believe Kai Krause's color picker also used a
Granger-style pattern.
--
Mike Russell - http://www.curvemeister.com
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