Black vs Black

[neil_se]

Sounds like you need better media profiles!

 

[Hotspur]

Light blue touch paper & retire...

So - no point choosing a CMYK vaue to give a particular black output.

Any RGB or CMYK value is converted into LAB by the rip and then turned into printer CMYK output, in which the black performance is controlled by the paper profile (ink limits and GCR settings)

The profiling guy would have set the max black your printer can produce by sending all the ink every printhead can throw out down onto the paper and setting a limit where appropriate (no bleeding, good drying etc)

Every combination of CMYK or RGB values in your file will be converted by the rip into its own CMYK values as close as possible to the required black as per the profile.

Thus if you find that on your profile a 50 50 50 100 gives a good black it wont translate onto another system necessarily.

Furthermore as CMYK and RGB are both turned into LAB by the Rip why does everyone who is only printing to inkjet use CMYK at all?

Every CMYK colorspace you select is that of a press you don't have! Discuss...

 

[AF]

Choose "Preserve Black" or equivalent in your rip profile and it won't convert 100k to brown.

 

[Bogdaniel]

So I just noticed something and maybe somebody can educate me on color. When you look at blacks, rgb is r=0,g=0,b=0, and cymk is c=0,y=0=m=0,k=100. Now both are black, and on corel palette, they are as black as they can get, but cmyk is not pure black. Can someone elaborate on why this is and explain the theory behind this.

Well on short certain printers require to use k = 100 others require to use a composition for black ( all 4 colors ) to get that intense black that sometimes we want to use. on my roland i use composition for black because the simple pure black is not black is something... if i remember right from class black that we all know and see all around is not k = 100. cyan magenta yellow key(CMYK) the key color is used in combination with other colors to create darker colors. When you print key 100 it doesn't ouput black.
An article explaining.

http://www.videolabs.net/uncategorized/cmyk-and-rgb-explained-for-the-rest-of-us/