Discussion

By Gordon Pritchard on Dec 02, 2016

It looks like they decided to go for maximum gamut - i.e. 20 micron FM screening, high SIDs in addition to the extra colors. I wonder if that's a very practical approach.

Interesting (and odd) that the C and M SIDs are the same (C: 1.85 M: 1.85)

The XCMYK test form they show in their introduction appears to be 4/C rather than 4/C +?

They also chose RGB as the extra colors rather than OGV that's used in, for example, Pantone's EG system. Why those RGB colors?

There's no mention of ink sequence.

So many questions....

By Gordon Pritchard on Dec 02, 2016

My mistake - it's just 4/c not 4/c plus.

By Barry Brown on Dec 09, 2016

I always have wondered a bit about CMYK+RGB. For example, solid areas in the red separation would be overprinting red areas produced by solid magenta and solid yellow. I think, that the luminance of those reds are degraded by those overlaying ink films, so that the colour space is nnot really expanded that direction. (The same would be the case in the solid greens and solid blue's.) I really can't see that CMYK+RGB truly expands the colour gamut, because some colours are at the same time being impinged.

CMYK+OGV,on the other hand, does allow narrow-band color separations, and solid-over-solid overprinting is not an issue.

I was always a fan of the old CMYK+CMY(K) method (which Crosfield's Tony Johnson called Hypercolour). CMYK+CMY(K) allows one to run the press at standard ink densities, just putting the paper through the press twice.
Benefits: No need for extra press units, no need to clean ink ducts, no need to change press settings.
The CMYK separations are best made 'achromatic', 'polychromatic /PCR', or grey-component-replacement/GCR (depending on who's terminology one uses), ie. the separation of the full-range black is such that the 'grey' component of quarter-tone through to shadow-tone colours is made-up mostly by two ink colours plus black.
The subsequent CMY (and optional second K) are separated with maximum Undercolour Removal /UCR, so those separations look pretty skeletal. They are there to add to the SID of the first print-run, so whereas the SID of C could have been 1,85, after the second print run it might be 2,30; M & Y equally incremented.
In my experience that really expands the colour space.
Some of the best CMYK+CMY printing that I've seen was done by the Helsinki printer Erweko, but that was many years ago now.

By Gordon Pritchard on Dec 09, 2016

Running CMYK at higher ink densities than standard (whether single hit or two hits) increases gamut due to higer saturation but does not make up for gamut issues related to ink hue and over prints. I.e. with CMYK you'll not achieve the oranges possible by using a, for example, PMS 021.
The issue with CMYK+CMYK is overcoming registration issues caused by running the substrate through the press twice. There's also the cost associated with running the same job twice. It's more efficient/effective to run the job once with inks at higher SIDs. There is a limit as to how high you can run the SIDs while increasing saturation and that is reached when the chromatic colors are about 35 points above standard.
The idea is not new. E.g. I did a blog post in 2009 ( http://the-print-guide.blogspot.ca/2009/01/printing-at-dmaxx-maximizing-cmyk-gamut.html ) about the method I developed and used at Creo in 1999. We called it DMaxx for Density Maximum.
What I'm concerned about is the initiative to formalize this method as an industry standard or specification especially using FM screening (you can do high SID printing with AM/XM screening)