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Re: [OM] More on monitors and printing

Subject: Re: [OM] More on monitors and printing
From: Jan Steinman <Jan@xxxxxxxxxxxxxx>
Date: Sun, 22 Feb 2009 17:37:15 -0800
> From: Andrew Dacey <frugal@xxxxxxxxxxxxxxx>
>
> I've actually seen screenshots from ColorThink (a program that maps
> colour spaces in 3-d) that demonstrate that some printers do have
> gamuts that extend outside of sRGB...

I think it's safe to say that ALL reasonable printers can print  
colours that are outside the s(tupid)RGB colour space.

Think of a "Star of David" -- two triangles on top of each other, one  
of them inverted. The points of one triangle correspond to red, green,  
and blue. The points of the other triangle correspond to cyan,  
magenta, and yellow. Light emitters (like monitors) use the RGB space;  
light reflectors use the CMY space. While it is true that most  
emitters' RGB space is a lot bigger than light reflectors' CMY space,  
it is quite difficult to make it large enough to encompass ALL the CMY  
space.

Combine this with the fact that s(tupid)RGB was designed by Microsoft  
to fit within the colour space of the crappiest $49.95 monitor that  
China could build, and it's not surprising that printers can out-gamut  
it, especially at the reflective primary "points" of the colour space  
triangle.

BTW, Andrew: good comment on "calibration" vs "characterization." I  
just gritted my teeth and ignored all the chatter about "calibration,"  
but if you really want to understand this stuff, it is important to  
understand the difference.

When you "characterize" a colour device, you describe it's response to  
stimulus, which is then saved as a "profile." When you have profiles  
for all your colour devices, you can decide on four different  
algorithms for making them respond to stimulus in as consistent a way  
as possible. That's another source of trouble -- if you set the  
algorithm to "vivid," for example, you might be expecting to get a  
"Velvia effect," when really you might be clipping the smaller colour  
space in order to have saturated business graphics for stuff like pie  
charts.

You should almost always set the rendering algorithm to "perceptual"  
for photographic image work. It will result in less exact colours  
overall, but little or no wildly different colours. Other rendering  
algorithms may give you highly accurate colour within the common gamut  
of the two devices, but wildly different colours outside of either  
device's gamut.

Colour management is not always simple nor obvious, but I must say,  
Microsoft has made it as difficult as they possibly could.

:::: You never change things by fighting the existing reality. To  
change something, build a new model that makes the existing model  
obsolete. — Buckminster Fuller ::::
:::: Jan Steinman, EcoReality <http://www.EcoReality.org> ::::



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