Something is already mentioned in the HP docs about the Quad formation and other black/grey ink combinations. The image quality (bleed/dotgain/detail loss) versus gamut size. I do recall another document where for the uncoated bond papers also combinations like MK + Grey ink only are mentioned, the image quality does not increase by using more diluted inks like the Light Grey. In the Quad formation (used on matte papers only) the PK ink is just an even darker grey ink than the Grey ink while it can act as a true Black ink on glossy papers. Some made the remark that the PK density on matte papers is already so high that it hardly does qualify as a Quad set, the PK partition in the tone range is short. However if you compare the ink densities of the Grey and Light Grey inks of the HP Vivera set to other third party Quad or Epson Tritone sets you will notice that the Vivera grey inks are also quite dark. I think this has been done by HP to lower the total ink load on the paper and by that limit bleeding etc, the more in color mode where less grey ink then can substitute a higher laod of composite crey color ink mixes.
The HP heads produce droplets of either 6 or 4 picoliter per ink channel, on average bigger than the Epson 3.5 or Canon 4 picoliter minimum droplets. The HP MK head makes 6 picoliter droplets, fine for Dmax but in the shadow details the PK head with 4 picoliter droplets is more suited if the paper coating can handle a higher inkload for a given density. This is complex, the MK ink will have larger carbon particles and more of them per ink unit. By that the chances are that the MK pigment particles stay more on top of the paper due to their size and the ink will bleed less than the PK on matte papers so the droplet size difference may not even compensate that effect.
Another factor is that while the PK, Grey and Light Grey inks are near neutral the MK is a bit warm, actually warmer than the Eboni MK ink that is the least warm MK carbon pigment ink. Usually we notice a color tone in blacks far less than a color tone in the shadows up to the highlights, so HP might have added the PK in the Quad formation to keep the neutral character as long as possible in the tone range and by that reduce the color ink additions that could influence the B&W print constancy in printing and in time (fading).
I'm sure there is more to write about the HP Vivera ink mixing philosophy, by me and much more by the former HP engineers. Think about the interesting absence of Cyan ink and the role Light Cyan and Green inks have to compensate that. For practice I would suggest to use the media presets that either HP or the paper manufacturers already made or suggested for the OEM and third party papers. I do not think we are smarter than HP engineers or the people at Hahnemühle, Canson, etc that provided the Z3200 media preset + profile files. Calibration and assigning another custom profile to that paper is still possible and I do that often but switching to other media presets where HM or Canson or HP made one available already is something else. The Ilford case is different today, some papers will be close enough to the old production with others I have my doubts.
BTW, check carefully whether HP Matte Litho-Realistic stays in production before devoting too much time on integrating it into your business. It does not help either that it is still delivered on 2" cores, the curl at the end of the roll of a 275 grams quite rigid paper is what makes me think twice on ordering it again. I used most of it for booklet covers in student design projects etc the off-white and smooth surface was in a sense unique, meanwhile Innova IFA 24 and a similar but slightly differently texturised Felix Schoeller product are more interesting, could be from the same source though.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots
Thanks very much for this excellent review of the ink set issues, Ernst. It is an understatement to say that there is alchemy behind the magic that is ink mixing with Vivera inks, and I am envious of your understanding of much of it.
Getting inside the printer, however makes me take issue about your other statement about how smart the engineers at HP were....
There is a lot to digest in your post, and I'm pleased you took the time to answer comprehensively - it will give me a lot to think about.
I wonder how, when using the Z Series printers and the embedded spectrophotometer, making custom profiles for papers that there is no road map for, no tested and determined or prescribed presets, such as exist with the Matte Litho Realistic paper, that we take our best guess according to the chart, because there has been no testing (such as in the case of Breathing Color Fine Art Papers) they admit they don't own any HP printers, that a project of experimentation ensues with each and every "out of the norm" paper. No guidance, just experience and the charts to go by. Given that the Quad ink set is available for many matte papers, I wonder if I found a roll of HP Matte Litho Realistic that was unlabeled in any way, if I might not be inclined to try a Fine Art More Ink Quad ink profile on it (especially given I had no knowledge of what it was)?
I respect what the engineers have done and how careful their testing is and how it reflects in the presets chosen for us, but I also respect the instinct of experimentation and my eye, when it comes to end results.
But shucks. HP is likely discontinuing yet another product, so the point becomes moot anyway.
We could apply this theory to another paper, however which is available, but with no apparent guidance on how to create a profile. Consider Epson Ultra Smooth Fine Art paper. One could use the HP Matte Litho Realistic preset to profile from, or do as I did, which was to also go for the Quad ink preset of Fine Art More Ink. I tried both, made calibrations and profiles using both, and I prefer the latter.
I do not think we are smarter than HP engineers or the people at Hahnemühle, Canson, etc that provided the Z3200 media preset + profile files. Calibration and assigning another custom profile to that paper is still possible and I do that often but switching to other media presets where HM or Canson or HP made one available already is something else. The Ilford case is different today, some papers will be close enough to the old production with others I have my doubts.
It is a dichotomy, it seems that certain 3rd party papers have specific guidelines, yet others do not. I have come to conclude that it is experience of having worked with the papers and ink sets that opens a door to getting to the right preset for the right paper for the right image. A professional printer simply could not exist this way, and requires using standardized methods of measuring and testing just to be able to stay profitable. It is a requirement.
An artist, however, without ownness to anyone but himself does not require such permission to experiment with presets, engineers be damned.
Still in all, don't misunderstand me, this is not to say that I do not highly respect your opinion in this regard, just that there is room for another approach to it, which no doubt is looked upon by some as folly, yet respected by certain others.
I can not possibly come to the level of technical understanding that you possess Ernst, and it is good of you to share your information so freely. To be able to have an open and honest discussion about how things work with these printers is often eye-opening for me.
It is when you discuss the ramifications of color ink mixing on fading, that my ears perk up. The question is just how much experimentation can one do before one crosses the line and breaks the "longevity chain" with custom presets?
Again, consider the papers that are available that have no preset models to follow.
I read in one of HP's documents that the "wrong" presets are possible to make, and it can affect the image outcome, but it is my understanding that they were addressing image quality rather than image longevity.
So if the answer is that if you use the wrong ink preset model on a particular paper with no preset model available, that it could fade prematurely, then what is a guy to do? Just not use and Lexjet or Breathing Color papers, etc?
If the answer is that one can just play with the presets making custom ones at will, then it's a matter of how long the paper and ink and carriage belts last....
