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By "the key component", I presume you mean the "K" (or "black", as in CMYK ), right?

If this is what you are concerned about, theoretically, ie, with perfect pigments, there is no need for the "K" component. Luminosity info is carried by the luminosity of each of the three CMY components, just like it is carried by the 3 RGB components in RGB color spaces.

It is only when one has to deal with real-world pigments that the "K" component is needed. It makes up for the propensity of real world C, M, and Y pigments to yield dark murky (sometimes brownish) blacks when mixed in equal (full) amounts. This limitation is why Photoshop provides both CMY and CMYK color spaces.

Another aspect of this is that there is exactly one conversion between an RGB image and a CMY image, whereas there are many different conversions between RGB and CMYK. This is one of the reasons why there are different printer ICM profiles for different printers.

HTH,

Tom

<blockquote data-quote="Tom Mann" data-source="post: 1533690491" data-attributes="member: 74903">By &quot;the key component&quot;, I presume you mean the &quot;K&quot; (or &quot;black&quot;, as in CMYK ), right?If this is what you are concerned about, theoretically, ie, with perfect pigments, there is no need for the &quot;K&quot; component.&nbsp; Luminosity info is carried by the luminosity of each of the three CMY components, just like it is carried by the 3 RGB components in RGB color spaces.&nbsp;&nbsp; It is only when one has to deal with real-world pigments that the &quot;K&quot; component is needed.&nbsp; It makes up for the propensity of real world C, M, and Y pigments to yield dark murky (sometimes brownish) blacks when mixed in equal (full) amounts.&nbsp;&nbsp; This limitation is why Photoshop provides both CMY and CMYK color spaces.Another aspect of this is that there is exactly one conversion between an RGB image and a CMY image, whereas there are many different conversions between RGB and CMYK.&nbsp; This is one of the reasons why there are different printer ICM profiles for different printers.HTH,Tom</blockquote>

[QUOTE="Tom Mann, post: 1533690491, member: 74903"] By "the key component", I presume you mean the "K" (or "black", as in CMY[B]K[/B] ), right? If this is what you are concerned about, theoretically, ie, with perfect pigments, there is no need for the "K" component. Luminosity info is carried by the luminosity of each of the three CMY components, just like it is carried by the 3 RGB components in RGB color spaces. It is only when one has to deal with real-world pigments that the "K" component is needed. It makes up for the propensity of real world C, M, and Y pigments to yield dark murky (sometimes brownish) blacks when mixed in equal (full) amounts. This limitation is why Photoshop provides both CMY and CMYK color spaces. Another aspect of this is that there is exactly one conversion between an RGB image and a CMY image, whereas there are many different conversions between RGB and CMYK. This is one of the reasons why there are different printer ICM profiles for different printers. HTH, Tom [/QUOTE]

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