Datacolor User to User Support Group.

I put a basic Granger Chart in the files section for fun and
experimentation.  A word of caution though.  Do not expect all colors
to be printed correctly.  Since it has been mathematicaly produced it
contains color combinations which no printer or monitor can reproduce.
 This makes it an extremely useful tool for detecting the limitations
of these devices.

Let me know how it works for you.

Thanks

Tom

I disagree. The rainbow is very unforgiving I don t think what everything the rainbow reveals should be taken literally but if you know how to use it, it s

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:

> Personally I wish Ed had never invented these &$%&$% charts, as they
cause 
> more confusion than illumination among users. I think the warning
above may 
> actually be understated, so I'll append my own: If you are printing
photographs, 
> use photographic test colors and images. Vector colors, especially
highly 
> saturated ones like Granger Rainbows, are not of this world, and
have little to do 
> with photographic color.


(laughing) 

Sorry ... they do serve a purpose but I can see how they would cause
massive confusion.

--- In colorvision_group@yahoogroups.com, "xun wang" <xun911@...> wrote:
>
> I disagree. The rainbow is very unforgiving I don't think what
everything
> the rainbow reveals should be taken literally but if you know how to
use it,
> it's wonderful tool to detect problems. So far the problems revealed
in the
> rainbow has been consistant with my test print.
> But I would suggest people to view the test shots -first-, then if
there is
> something wrong with the color or tone, verify it with the rainbow.
> 
> To say it'd better not been invented is a bit unfair.
> 

I would say the rainbow is extremely unforgiving.  Its like having a
chainsaw ... be careful where you use it :-)

In a message dated 3/15/06 2:49:06 PM, xun911@... writes:

> I disagree. The rainbow is very unforgiving I don't think what everything 
> the rainbow reveals should be taken literally but if you know how to use it, 
> it's wonderful tool to detect problems.
> 
> Well, given that Tom has posted, as he calls it, a sharp chainsaw in the 
files section, perhaps a bit of description is in order. Granger Rainbows are 
cross-color gradients   in flat 2 dimensional image files. Since all the colors 
have one or two of the RGB channels maxxed out, they represent full color 
saturations. The gradients are basicly the "skin" of the RGB color space they are 
displayed in. They show nothing about the inside of the colorspace (where 
photographic colors live) but only define the extreme exterior.

I like to describe a 3d graph of an ICC profile as being like a bronze statue 
of a tornado; yes, it shows a familiar form, but its all about the surface of 
the tornado, when the important stuff is happening way inside. Granger 
rainbows take this superficial focus on the skindeep to a new dimension, by focusing 
our attention on how things look at the surface of a profile only. Few if any 
of these surface colors will ever be reached by photographic content; many 
cannot be reached by the monitor they are shown on, or the printer they are pri
nted on. They are in the land of vector art and artificial colors. With a 
Granger rainbow as the active window, do a Custom Proof Setup command in Photoshop, 
and choose your monitor profile. Then select the gamut limit command, and 
watch the entire rainbow disappear... its all out of gamut. Do the same with a 
matte printer profile, and you'll lose nearly as much. A gloss profile has 
marginally more or the colors in gamut.

I often see composite test images, where half the page is devoted to 
synthetic gradients and Granger rainbows... odd, since the goal is to print good photo 
color, and there is almost no overlap between these synthetic colors, and 
photo color, or for that matter, printer color. So yes, there is a purpose to 
Granger rainbows, but it is nearly as abstract as the rainbows themselves, having 
mostly to do with out of gamut colors, gamut limits, relations between 
workingspace gamut lines and printer gamut lines, etc...

C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com
>

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:

> Granger rainbow as the active window, do a Custom Proof Setup
command in Photoshop, 
> and choose your monitor profile. Then select the gamut limit
command, and 
> watch the entire rainbow disappear... its all out of gamut. Do the
same with a 
> matte printer profile, and you'll lose nearly as much. A gloss
profile has 
> marginally more or the colors in gamut.
> 
They also give a superficial view of how out of gamut colors are
mapped by different rendering intents.  I believe this is more a
function of the Color Management Module (CMM) engine than an
indication of how good a profile is.

Disclaimer:  I don't have my color scientist lab coat yet.  Working on it!

... Just to append on what David said. It s not exactly the surface of the color, but rather the fully saturated version of the color. I like to think of the

Tom, I just checked out your uploaded rainbow. it s not quite right. I ve uploaded a correct one named GrangerRainbow . ... -- ... xun911@gmail.com 

--- In colorvision_group@yahoogroups.com, "xun wang" <xun911@...> wrote:
>
> Tom, I just checked out your uploaded rainbow. it's not quite right.
I've
> uploaded a correct one named "GrangerRainbow".

Thanks ... what was off?

just because mine was prettier...:) if you re into test charts & tools, here are some for download - 

--- In colorvision_group@yahoogroups.com, "xun wang" <xun911@...> wrote:
>
> just because mine was prettier...:)
> if you're into test charts & tools, here are some for download ->
> http://www.colorremedies.com/realworldcolor/downloads.html
> 

They look identical to me.

look again... ... -- ... xun911@gmail.com www.xun-wang.com