Hello. I try to work with the node "Make CMYK Color". I want a Green like this (Photoshop): photoshop

On Vuo, I take the CMYK node, and the green result is not good:

vuo The HEX color must be #45aa56 and not #44ff30.

Is it a bug? or a false use of this node?

Comments

There are different ways to

jstrecker's picture
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There are different ways to convert between RGB and CMYK.

In Photoshop, the method depends on the color profile you've chosen for the document.

In Vuo, the method is always a linear formula ((1-C)*(1-K)). This is the same one used by http://rgb.to/hex/44ff30, for example.

A different site, http://www.codecrete.net/CMYK, which uses the ISO Coated v2 300% Color Profile, gives a result closer to what you're seeing in Photoshop.

If you're interested in Vuo supporting more than one color profile, you're welcome to create a feature request.

Good point @JérômeLanon ;)

Bodysoulspirit's picture
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Good point @JérômeLanon ;)

In Vuo, the method is always a linear formula ((1-C)*(1-K)). This is the same one used by http://rgb.to/hex/44ff30, for example.
A different site, http://www.codecrete.net/CMYK, which uses the ISO Coated v2 300% Color Profile, gives a result closer to what you're seeing in Photoshop.
If you're interested in Vuo supporting more than one color profile, you're welcome to create a feature request.

Thanks for the explanation Jaymie.

Yes, with my little understanding of the color world, it seems CMYK mainly exist because of the printing methods.
So by default I would have rather preferred a generic CMYK color profile rather then a (1-C)*(1-K) method.
Because even if it would not have covered all the subtle printing results, it would still have matched a printing result more then (1-C)*(1-K).

I see very small use of CMYK use for a RGB like gamut.
But perhaps I'm very wrong, and a wide range CMYK gamut is useful for Pantone conversions / matchings.

Perhaps a small addition to the node without a Feature Request could be an option for either (1-C)*(1-K) or Generic Printing CMYK, and a Feature Request for a larger profiles options.

Gonna create that Feature Request ;)

I don't think this has much

MartinusMagneson's picture
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I don't think this has much to do with color spaces, rather color selection. The color in photoshop have a K(N) value of 0, which when using CMYK in VUO will render a fully saturated and bright color. It seems like Photoshop derives the grey value for the top 3rd of the spectrum from the amount of CMY, then starts exponentially adding K(N) from that point until reaching K(N) = 80 to 90 at the bottom (totally black). You can either adjust the black level manually (which probably won't produce the same color):

Or use a Make Hex Color node to get the desired result: