rich black for cmky inkjet

[Pondering]

I'm just wondering if anyone has any suggestions for a rich black for use in cmyk inkjet printing, specifically four inks and not the newer six or eight ink printers, i.e. do you go with 40-40-40-100 or do you prefer just 100 percent black (0-0-0-100), and why? thx!

 

[Stephen Marsh]

If you are printing with say an Epson printer driver direct to the printer with no RIP, then it does not matter and the input data is/should be RGB.

If you are using an inkjet RIP, then you may be able to input CMYK data, however it is still likely going to be transformed through an ICC profile's PCS and the input values will likely be re-separated to the output device CMYK profile. Some inkjet RIPs can perform devicelink profile type moves that may retain some of the source file CMYK data intact when using ICC profiles (or one may use a devicelink profile which may preserve some CMYK values).


Stephen Marsh

 

[Pondering]

Thanks. I think it's an HP printer, and I'll have to see about the RIP. I'm guessing it's software based. I was just wondering if the are any "rules of thumb" for inkjet printing of rich black (or if it matters that much) since most of what I am finding seems geared to offset. Also, I am referring to vector graphics set up in cmyk. Maybe I should just see about getting a test swatch of different options done.

 

[Stephen Marsh]

Pondering, yes, I would output an RGB vector object with 0r0g0b values - this should be as dark and neutral as things get.

Then you could compare with various CMYK rich black builds, to see what values produced a dark and neutral result.


Stephen Marsh

 

[Mike F]

Depends on the printer and RIP you're using I would imagine. With the Roland Versacamm series using the VersaWorks RIP, you're supposed to use RGB along with the Roland spot colors they provide you. Couldn't say as far as other printers or RIPs.

 

[Correct Color]

Actually, it's pointless to even try.

Reason is that when you're creating any color value in CMYK or RGB, you're creating in some CMYK or RGB color space. And at some point somehow, unless you're working in your exact final destination color space, you've got to transfer your color values to that color space.

And whether you use a RIP or don't use a RIP, the conversion still works pretty much the same way, which is that the engine making the conversion isn't going to care anything at all about the CMYK value you send it, other than what the L*a*b* value of that CMYK value is either in the color space in which you created it, or in what it's been set up to assume is the incoming color space.

It's then going to convert look for the corresponding CMYK values that most closely match that L*a*b* value in your destination color space (printer profile) and that's what you're going to get. And, if it turns out --as is often the case -- that your printer has a much deeper black point than the black point of your CMYK working space, you'll wind up with a pretty weak looking black.

That's one of many reasons why it's not a good idea to send CMYK files to large format printers, and why -- as others have said -- R=0, B=0, G=0 basically tells the device to print at its ink limit, so that's the best way to go.


Mike Adams
Correct Color

 

[onwsk8r]

Actually, for a 4CP printer, 100/100/100/100 would tell the printer to lay down the most ink; RGB0,0,0 is like 350% coverage, the 4x 100's would be 400% coverage. Your RIP/printer might limit max coverage, so it might scale things back. In my experience, this type of feature is not documented.

Printing RGB 0,0,0 will NOT necessarily give a neutral black. It will if you're using a good rip, though.

That being said, let's talk about substrate. If you're printing on anything paper-y, you'll be best to stick with pure black because you'll get ripples with heavy coverage.

If you're printing on high quality (not paper) inkjet-type media, you could go with one of the standard rich black recipes - 40-40-40-100 or 60-40-40-100 etc.

To the point, if I'm printing on anything resembling uncoated paper, I'm pure black all the way.
If I'm printing on synthetic materials like vinyl or poly I'll use 60-40-40-100 (my fave rich black)
If I'm printing on canvas, I might use 100-100-100-100 because the canvas can handle the extreme coverage.
If I'm printing on something I shouldn't be running through an inkjet (coated paper, non-inkjet media, etc), I'll use pure black so it doesn't smear/offset

Really, it's all in the media.