RGB to CMYK - Deep Blacks?

[Scarfy]

Hi All,

I've found the RGB to CMYK conversion very useful for sending stuff to printers.

But I was wondering if anyone knows how I can achieve rich or deep blacks.

The other colours come out fine, but the blacks tend to be grey-ish.

The command I'm running is,

convert -verbose source.png -colorspace CMYK output.pdf

where source.png is an RGB PNG file and the output is a PDF.

Thanks,

Steve

[anthony]

Printers do not just need CMYK colorspace, they need a very specific color profile, that not only depends on the printer but on the paper being used as well.

It is a very complex bussiness, and beyond my skills at this time.

[Scarfy]

Ah, okay.

This is for sending PDFs to Lulu (the online printer / publisher).

They say they accept RGB PDFs, which they can convert to CMYK, but the print colours are often dark and subtle colours are lost. Converting to CMYK myself helps, save for the blacks.

I'm actually using another command now,

convert -verbose cover01.png -fill "rgb(0,0,1)" -opaque "rgb(0,0,0)" cover01.png

to make the blacks a very dark blue, instead. This makes better in the PDF previews, where they now actually look black, but I have yet to print it and see how it looks.

Thanks for your help, though.