# CMYK Colour Gamut?



## Stitch-Up (May 26, 2007)

Hi guys

I don't know whether all DTG printers use CMYK inks but mine does and so I took a look at the CMYK colour gamut today.










Does using CMYK ink system mean that the colours we can accuratly produce are those withing the gamut? If so, it seems very restrictive and I know I produce a greater colour range than that in the picture above - I'm assuming the RIP is responsible for the accuracy of the colours outside the CMYK gamut? Or am I missing something fundamental? 

Cheers

John


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## EricDeem (May 7, 2011)

CMYK has a gamut of over 16 million colors. Your monitor being RGB cannot display all the colors so it appears as though the gamut is smaller then it actually is.


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## zoom_monster (Sep 20, 2006)

John,
The picture is just a relative representation. CMYK is very restrictive, that's why we have Pantone colors and why Epson head are built with so many channels (they did not build them for white.. )

Because inks are translucent and produce the color we see by subtraction of reflected light, it's simulation of what we would see in "the real world". We can saturate colors to give more pop and drama, but in doing so we are limiting subtle steps between one color and the next.

On high end printing, if you want more color and depth you have to add color (hexachrome, spot color etc.)

If you Google Process color or CMYK, you can see that it's pretty old technology. Inks are better and improving, and there are tricks(software, perceptual) and special ink sets, but CMYK theoretically can never be perfect.


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## kevrokr (Feb 26, 2007)

I know that DuPont CMYK inks have a larger color gamut than regular CMYK process inks.


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## EricDeem (May 7, 2011)

Oops I was wrong...RGB produces 16 million colors (256x256x256) and cmyk produces 4 billion (256x256x256x256). This is atleast how I understand it to be.

I think the DuPont inks allow for the white ink to be counted too, which enlarges the gamut even more.


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## kevrokr (Feb 26, 2007)

Dekay317 said:


> Oops I was wrong...RGB produces 16 million colors (256x256x256) and cmyk produces 4 billion (256x256x256x256). This is atleast how I understand it to be.
> 
> I think the DuPont inks allow for the white ink to be counted too, which enlarges the gamut even more.


It doesn't quite work out that way...the RGB color gamut is much larger than the CMYK gamut because it uses light rather than reflection to represent it's hue. Further, the color spectrum that is visible to the human eye is much larger than both as the illustration John posted shows.


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## EricDeem (May 7, 2011)

kevrokr said:


> It doesn't quite work out that way...the RGB color gamut is much larger than the CMYK gamut because it uses light rather than reflection to represent it's hue. Further, the color spectrum that is visible to the human eye is much larger than both as the illustration John posted shows.


Very interesting. I learn new things everyday here, information on this very subject is hard to find and when you do it always seems to be conflicting. Thanks for breaking it down like that.


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## zoom_monster (Sep 20, 2006)

kevrokr said:


> I know that DuPont CMYK inks have a larger color gamut than regular CMYK process inks.


Hi Kev, as you know for screen printing ink some manufacturers have "warm sets" and "cool sets" with slight variations of the red/blue and green/yellow balance.

If you tweak the ink to give a better "XXred" you will do so at the expence of something at the exact opposite of the color wheel. It's pretty easy to create colors from nature, It's just imposible to do it with 4 components.

I propose that inkjet technology print small self charging nano LEDs directly on to the substrate


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## kevrokr (Feb 26, 2007)

zoom_monster said:


> If you tweak the ink to give a better "XXred" you will do so at the expence of something at the exact opposite of the color wheel. It's pretty easy to create colors from nature, It's just imposible to do it with 4 components.
> 
> I propose that inkjet technology print small self charging nano LEDs directly on to the substrate


I could see chasing your own tail trying to balance different colors from different inksets to have certain color inks look pleasing without doing too much mixing in regards to screenprinting...it's all spot colors. I've done something akin to this before to get paints to match Pantone colors for a display company I worked for years ago. Sometimes you end up with a useless, muddy mess.

SGIA does an equipment assessment every year and we were able to see how different RIP softwares handle the ink gamuts. DuPont's ink is able to go just outside of the CMYK gamut in the greens and purples when handled correctly by the RIP. When you get into some reds, pinks and yellows, the gamut was not as full as US SWOP, but with some crafty profiling, most RIPs should be able to render colors that are pretty close.

I like the idea of the Nano LEDs...


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## zoom_monster (Sep 20, 2006)

Another thing that limits "gamut" is how white the substrate is and also how textured it is. Glossy magazine stock will have a better range of color than newsprint, but even that is not perfect and they (publishers) will have to add what they call bump plates to have the most pleasing colors. Next time you buy a box of cookies, look at the color targets on the hidden flaps of the box. You will see that they use a spot/process hybrid and often include 6 to 8 colors.
Epson, HP, Canon etc allworked on ways to improve. If they were able to get all colors with 4 inks, they could have concentrated on that and finer resolution to get better color, but then gave that more channels and tweaked colors was more effective to that end. We settle for CMYK because of value not because it's the best


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## cavedave (Dec 5, 2006)

Its not a case of RGB being bigger than CMYK or visa versa, I can show you examples of CMYK gamuts being bigger than RGB and RGB being bigger than CMYK. 

In general RGB and CMYK gamuts are different, there is a bunch of colors they can both reproduce and then each has areas of color reproduction that the opersite struggles with.
For example view green on your screeen with no color matching on (0,255,0), this cant be reproduce using CMYK very accuratly.

DTG printing on T-shirts have a very small color gamut, but even this isnt consistent, when you print directly onto a white shirt the color gamut is much smaller than printing onto white ink on a black shirt.

Size of the color gamut you cant do much about, direct onto white t-shirts has a small gamut and unless you want the cost of printing white ink first there is little you can do to increase this (multiple passes of CMYK does help a lbit), but you get to the point where it is what it is.
What then becomes really important is the gamut mapping, this is how you deal with out of gamut colors and also gettingt a good preview on screen, so you know that green isnt going to print correctly.

The RIP does deal with the out of gamut colors, but you should actually think of the RIP as multiple components, one fo which is the color managment and in any professional level product these will be using ICC profiles which are a standard format as defined by the ICC consortium INTERNATIONAL COLOR CONSORTIUM
When you link two ICC profiles (such as going from sRGB to the CMYK for a white t-shirt) you select a rendering intent (which is how the out of gamut colors are dealt with), which again is defined by the ICC, see Introduction to the ICC profile format section 3.

The whole point of this is that it doesnt matter what RIP you use (or CMM = Color manament module that runs the ICC part of the RIP) the results of using two ICC profiles with a selected rendering intent will be the same.
Note: This doesnt mean using the same ICC profiles in two differnt RIPs will give the same result, as in general it wont. But not because of the ICC profile process, this is down to different transfer curves and screening systems used. The ICC profiles shouldwork the same and give the same in that component of the RIP as its a standard.

Depeing on the RIP, you should be able to control both the input profiles you are using and the rendering intent.

What I am getting at is while the RIP deals with this, you should have (as an end user) on a good RIP, quite a bit of control over how this process works for you.

Best regards

-David


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## scuba_steve2699 (Nov 15, 2006)

lots of good discussion on this thread - I would like to see it continue to expand. Here is a webinar i did last week going over some color basics. I hope it helps!

[media]http://www.youtube.com/watch?v=_O5hmrzu0zA[/media]


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## Hegemone (Oct 18, 2011)

kevrokr said:


> It doesn't quite work out that way...the RGB color gamut is much larger than the CMYK gamut because it uses light rather than reflection to represent it's hue. Further, the color spectrum that is visible to the human eye is much larger than both as the illustration John posted shows.


That's an interesting concept. How is the RGB gamut represented on paper that cannot produce light but rather only reflects light? How is CMYK represented on a LCD screen that only has red, green, and blue pixels but no black pixel?

Not to be rude but this discussion seems to be mixing a lot of color theories and representation issues into one thread. Screen representation, print representation, light, pigments, hue, saturation, color temperature, lighting temperature, absorbtion, and reflection.

Its not simply a matter of CMYK can represent more or less colors then RGB. More specific questions need to be asked. Otherwise its really easy to get lost in misunderstandings.

The later posts are much more complete and specific which is good.

My two cents. Toss them in a well and make a wish.


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