HP Designjet Z-2100 Z-3100

Amid conditions of great secrecy, one hundred of the photographic world’s shakers and movers were assembled in Barcelona a few months ago and (with considerable razzamatazz) introduced to Hewlett Packard’s new babies, the Z-Series of Designjet wideformat printers. They were recently unveiled to the public at Photokina.

To some extent they are a natural progression from the 9810, A3+ printer, which was UK launched at Focus this February, with its long-life Vivera ink set. However, a key element of the Z-series is the expansion of the ink set to 12 slots and the built-in colour management facility. The machines have been built around an X-Rite Eye 1 spectrophotometer to deliver a truly hands-off colour calibration and profiling. And we do mean hands off – you need five clicks of the mouse, then go for a cuppa while the machine gets on with the job. In 20 minutes it will have built a linearisation curve, made a profiling target, allowed it to dry and then sucked it back under the bonnet to build a bespoke profile. Although 35 HP paper media are currently available, the bespoke nature of the profiling means you can take any third-party media and achieve great accuracy, almost immediately.

The units are currently available in 24” and 44” with either a 12-ink set or an 8-ink set. The ink configurations are shown in the table. The 12-inks systems have yet to arrive in the UK. We used the 12-ink version in Barcelona and the 8-ink version at the DCP open day more recently. The Gloss Optimiser (E) is available only for the 12-ink systems. Glop is placed in varying proportions, determined by the image and print driver. The driver brings the white down and the colours up to meet it, to preserve the tone balance in the picture. Glop is used at roughly the same rate as the other ink cartridges and its usage is image dependent.

Printing may be carried out in full colour or black and white modes, the latter only using the neutral inks. In order to help preserve neutrality in the greys within an image, the driver picks up on the pixels which are close to neutral and backs off the coloured inks in those areas. Metamerism is claimed to be very low and the ink engineers we discussed the subject with revealed the lengths that HP have gone to so as to minimise the effect. There is always a balance between the long life of pigment-based inks and metamerism and the Vivera inks have certainly pushed the boundaries on fade-resistance. Henry Wilhelm was present in Barcelona and reported verbally that the fade resistance of the ink set has passed the 400-year mark. Print speed is good and we measured an A3 at ‘Best quality’ at 5m 08s in Barcelona on a prototype machine. The quoted figures are 15min for an A1 page, equivalent to 17ft2/hr at best quality. The droplet size is 4 pico litres for the lighter colours and 6pl for M,Y, MK, R, Gn and B. The droplet delivery is thermal which HP claim leads to reduced ink wastage during head cleaning. The chamber of a thermal head is 40 times smaller than piezo. The availability of the green ink means that the Z-series need to employ less ink to obtain the extreme parts of the colour gamut, leading to reduced ink loadings. Cartridges are 130ml although the 24” machine arrives with a one-off set of 60ml cartridges. The print heads are replaceable, self aligning and ganged for two colours per set. Nozzles are checked on the fly and there is built-in redundancy to keep things moving along even when some nozzles have clogged.

The technology we were shown at HP’s Barcelona R & D labs for studying droplet dynamics was fascinating. A high-speed strobed laser is used to illuminate the print head operating under a microscope, so that the shape and trajectory of drops flying through space can be studied, very clever indeed, as was much of the technology we were shown. An enduring impression we gained from spending so much time with the Spanish development team was their boundless enthusiasm for their new baby!

The driver interface reports on the ink and paper usage for each job, useful in a busy bureaux if you need to cost jobs on an individual basis. These data may also be exported to Microsoft Excel for additional cost accounting, a neat feature.

RIPs

The RIP developers have been on-board with HP development engineers for some time and so we can expect a whole lot of solutions to become available very soon (some are already here). Importantly, the highly regarded GMG RIP is well into its development cycle, especially important for proofing high-quality press work. Media HP currently has 35 types of media in their catalogue. This includes four canvases, a bunch of glosses and lustres, along with a lot of Hahnemühle art media (HP and Hahnemühle, quite apparently, have a close working relationship). They also have compatible vinyls, films, outdoor papers and scrims. Paper thickness can be up to 0.8mm or 500gsm. This struck us as a little on the thin side as it would be nice to load pre-prepared board for many applications. Paper feed can be as flat sheet or from the rear-mounted roll. You must have access to the rear of the printer to load rolls of paper.

Colour Testing

Sadly we were only able to test the 8-ink system at DCP, the 12-ink models have yet to arrive in the UK. DCP had already run a profile for their own-brand silk paper and so we used that for our initial analysis. We were particularly keen to examine the metamerism. Visually the print was excellent; the greys matched the base white of the paper, which contained brighteners. The gradations were smooth and the greyscale linearity graph was typical of a profiled output, just blocking the shadows at 20 RGB points. The image stayed neutral in natural, north daylight and a D65 viewing booth. In low energy light (the poorest around!) the greys were pushed towards magenta, a fairly typical effect. Looking at the statistics, the gamut volume measured at 754,000 units. For comparison, we have been getting around the 800,000 mark with Epson K3 ink on various papers. The best results obtained with Epson K3 were on their Premium Lustre (855,000) and we achieved 779,000 on the Ultrachrome ink set of the 7600. The differences are actually quite small and there seemed to be some room to increase the Dmax and grab back some of the deficit of the HP with profile tuning. One of the absent features on the Z-series software is profile tuning and editing although, for the vast bulk of users, this is an area into which you would not wish to tread!

The overall colour error measured at 5.0 Lab ΔE, 3.2 ΔE2000. The average we obtain during bespoke profiling is 3.3ΔE2000 (that’s from just short of 1,000 printer/paper combinations) so the benefit of on-board colour management is immediately obvious – you are more or less guaranteed top-level performance from the built-in control, even with third-party media, for which there would ordinarily not be a bespoke profile. The only people who would need to take further measures are the pre-press and contract proofing guys who have to get down to 2 ΔE2000 to comply with standards such as the PPA ‘pass4press’. The data quoted on the HP product sheet for both 12-ink and 8-ink machines are 95% of colour within 2.8ΔE2000 and a median value of 1.6ΔE2000. The printto- print repeatability of colour is quoted at <0.5ΔE2000. We might expect to obtain better results from the larger gamut of the 12-ink set, but only testing will tell. Certainly, when we tested an Epson system with CMYK+RGB inks we pushed the gamut out to a record 889,000 so we can hopefully look forward to similar expansion from the Z-series with extra inks.

Metamerism

Having had ‘improved metamerism’ pushed at us by the marketing and technical staff from HP and a smattering of quotes in the product literature, we were particularly keen to get some numbers together. This is a fiendishly difficult area to pin down, even with quality instrumentation. Metamerism varies around the gamut and its perception is dependent upon the closeness of the colour to neutral grey as well as the light quality and, quite strikingly, by the size of the print. Something that looks OK in a small swatch may not look so good in a 20x16 monochrome print – we discuss this in some detail in Paper Chase this issue, a piece that was written before we had even seen the new HP. We therefore followed the same testing methodology of tracking the metameric index down the tone scale and then around the colour wheel, close to the neutral point of the base paper. We would dearly love to be able to hold a single number before you and say yes or no to the difference in metamerism between say the Epson K3 UltraChrome and Vivera. One thing however readers should not lose sight of – the fact that we are having to go to such lengths to differentiate indicates just how good the modern inks are!

The starting point is to examine the spectral power distribution (SPD) of the grey. At this point the UltraChrome seems to hold the advantage, certainly at the nominal 50% grey we were measuring. The bumpier the curve, the more scope there is to create metamerism, indeed you have to cross a ‘flat line’ grey (such as the Q13 swatch) three times for metamerism to exist at all. In the graph, the Kodak Q13 swatch is essentially non-metameric (the X-Rite instrumentation gave readings of 0.3 Q13, 1.3 K3 and 3.5 Vivera, the graph shows three setsof reading superimposed to show that the measurement repeatability variations are effectively zero).

Measuring the metameric index around the colour wheel, but close to the neutrals, produced closer results. The index increases as you move further from neutral and this enables us to plot the index against the colour component of error in the neutral value. The straight-line graph then allows us to calculate what the metamerism might be in a perfectly neutral print, ie the lowest possible value. This works out at
2.32 for Vivera and 2.21 for UltraChrome K3 again giving the K3 a very slight advantage. How this will change for the 12-ink set will only become clear when we have the opportunity to carry out detailed tests. Similarly, we would expect different results if only the black inks were used – however, with our reader’s inclination to make album pages, mixing both colour and monochrome on the same page, all-black inks are not an option anyway. The jury will return in due course!

Overall

These Z-series represent a valuable addition to the market place, they will spur the existing manufacturers to respond and the competition can only benefit the consumer. The ability to produce calibrated conditions with no specialist expertise from the user will delight a huge chunk of the user base, especially the art printers, who always want to feed their own favourite paper into their workflow. The absence of a 24” machine is a little puzzling especially as it is the big seller in the UK market, maybe everything is bigger in the States! As to the 12-ink set, we can’t wait to get our hands on one; it has just got to be even better.

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