4/9/2007: The Testing Begins...
During this initial week we have been printing on the HP Instant Dry Glossy and the ID Satin finished photo papers. Each a nice 260 gsm (grams per square meter) paper with the weight and feel of many traditional wet chemistry photo stocks. Using these papers has provided an opportunity to test another feature designed into the Z3100 -- the elimination of bronzing through the application of what HP calls a gloss enhancer.
Bronzing is a visual phenomenon that occurs when printing on glossy papers using an inkjet printer. It is called bronzing because it imparts a metallic bronze-colored sheen to areas of the print. In my mind's eye, the strictly non-scientific explanation for this is that as light passes through varying thicknesses of ink, then bounces off the paper's glossy sub-coating the light is phased and gets scattered and bent. Bent light means some weird color effects will occur, hence rainbows and bronzing, which becomes most evident when looking at an inkjet print from extreme angles.
HP's Gloss Enhancer is a clear liquid (not really an ink) that eliminates bronzing by evening-out (enhancing) the glossy quality of the ink to make it more uniform. Gloss Enhancer is automatically disabled when printing on matte art papers because the bronzing problem occurs only when using glossy or semi-glossy substrates. Since the gloss enhancer goes down and mixes with the rest of the inks, HP is quick to point out that the gloss enhancer is not a top coat or sealant. But, it does totally eliminate bronzing.
Which brings up the question: to bronze or not to bronze, or as Pat Morita fans might say, Gloss On, Gloss Off? If you review the events that Hewlett-Packard sponsors and in the majority of the promotional material published about the Z3100, it is clear that digital photographers rule. And why not? This is the huge and continually growing market that has driven digital imaging since the beginning. HP has committed much research and effort and five of the twelve inks in the Z3100 system to getting photographic prints -- whether they be black and white or full color -- right. Therefore, they are very proud of getting rid of bronzing.
Needless to say then, it is a bit amusing to see an HP engineer's chin drop when a digital artist picks up a black and white photo print and says they think the bronzing effect is "rather interesting." As did my friend Helen Golden during one of the print comparison sessions at the HP labs. The dumbfounded silence in the room was nearly palpable. Here was a roomful of engineers who had spent years chasing around "the bronzing issue," which had no doubt been like trying to herd cats into a wading pool. How could she say such a thing! But, here is a perfect example of the difference between a digital artist and a digital photographer or an artist and just about anyone else for that matter. Where one sees an imperfection, the artist sees an effect that, in the right context, could be useful or at least interesting. With the Z3100, the point is that the bronzing "imperfection" has been eliminated, while the bronzing "effect" can be accessed and employed if that is your desire. And who can argue with more access and control.
One thing that my digital art testers have agreed upon at this point is that with the printer's complement of Gloss Black ink, Matte Black ink, Gray ink, Light Gray ink and Gloss Enhancer, the Z3100 produces remarkably neutral black and white images. This is true whether I turned Print in Grayscale on or off while printing a black and white image. With the Z3100, if there is going to be a greenish cast or other color tints in a black and white print it is either because the artist/photographer used HP's Gray Balance (tinting) function (see image below) or has created that image to display those color tones. The savvy reader will note that since both Matte Black and Glossy Black inks are on-board, the Z3100 can print on either glossy or matte paper without flushing ink systems or any kind of delay for that matter.
ABOVE: You can add and control color tinting of a grayscale image in the Z3100 printer driver.
Since glossy photo papers are known for their image sharpness and clarity, I had the opportunity to test something with the group that I had long suspected but could finally prove. Over the years that we continued printing artwork on the CP2500 Designjet, Myriam and I saw many new printers come to market boasting 1200 dpi (or, beyond) printing capabilities. You could infer from this that the higher the dpi (dots per inch), the greater the resolving power and therefore the more detail in the resulting print. But, having worked in television production all these years I know that things such as sharpness, resolving power and detail are slippery subjects not often related to the ability to see more information, but rather how the visual information you have is presented. The fact that there are more dots of ink rendering the same number of pixels per inch (ppi) did not compute to me as increased resolving power. And, yet some of these new printers did seem to produce clearer imagery. In order to test this, I sent the artists samples of one of their image files printed on the Z3100 at both 600 dpi and 1200 dpi asking if they could see any difference in the ability of either print to resolve the fine details in the image.
Much to the amazement of some, there was unanimous agreement that there was no difference between prints made at 600 dpi versus 1200 dpi. One HP engineer had told a webminar I attended this very thing: "1200 dpi is not necessary unless you are perhaps printing a document with text that is under 6 pts." Sorry, but my eyes cannot resolve print under 9 pts. And the only people using 6pt. type, that I am aware of, are doing so exactly because people cannot actually see what is there, for example drug manufacturers who now have to list all the awful side effects of their latest miracles. But, why are prints made on the more recent line of printers markedly clearer? As it turns out, this is more a function of variable dot size printing and not increased dpi.
Variable dot size enables the printing mechanism to lay larger dots in large areas of saturated color where one would expect to need more ink and smaller dots where colors are blending or transitioning into light or white areas of a print. Some of the dots can be as small as a human hair. This minimum dot size allows a thin, even mist of color to be applied in areas where fine detail is being rendered. This is like the difference between trying to draw a thin, light line with a 2B pencil versus a 6H pencil. While printing at 1200 dpi does not increase the ability for the resulting print to resolve fine detail, the minimum dot size does create a much cleaner image.
To illustrate this to myself, and now you (in image below), the same tiny area from two prints of the same image file has been scanned and enlarged and placed side by side. Both prints are of the same 200 pixel per inch (ppi) image file and both were printed at 600 dots per inch (dpi). The same amount of detail can be seen in each; that is, the signs can be read (or not) equally well in either image. But, the image on the right was printed on the Z3100 with smaller ink dots resulting in a much cleaner image. This essentially tricks the eye into imagining that one picture reveals more detail than the other. At a normal viewing distance both prints match quite well, but once you have seen this up close, could you ever go back to printing without variable dot size?
ABOVE: On the left a 600 dpi print from the HP 2500; on the right a 600 dpi print from the HP Z3100. Both have the same amount of detail or resolving power, but smaller dots make for a much cleaner image.
Why, then do we continue to see inkjet printers boasting more and more dpi? One reason has to be that we live in a culture where bigger and more is automatically considered better. In this climate it would be foolhardy not to produce a printer with a lot of dpi, since more dpi is much easier to sell and comprehend as being somehow better than it is to try and explain the advantages of variable dot size. Does this mean that I will only be printing my work at 600 dpi? Nope. But, not because of increased resolution.
Instead, printing at 1200 dpi on the Z3100 has other advantages. Here are some variations in the Print dialogue window of the Z3100 that I have been using for this test (see images below). Under Paper Type/Quality the settings Best and Maximum Detail evoke 1200 dpi printing. More Passes is automatically checked On, and this guarantees that banding and other printing artifacts do not occur. Since employing these settings does not use more ink and adds only time to the printing process, one would be foolish not to use this mode for finished printing. In the Print dialogue window, by selecting Best and leaving Maximum Detail un-checked but turning Extra Passes On, a 600 dpi print with no perceivable difference from a 1200 dpi is made. This saves a bit of time, which is important if you are tweaking a file and working toward establishing a finished print. For purposes of making the quickest proof at 300 dpi, set the Quality Options to Standard and move the slider over to Speed (see bottom of image pair below). For a final print, however, there is no question that you give it the time and all the best that a printing system has to offer.
ABOVE: These settings in the printer driver result in 1200 dpi printing requiring more time but yielding the highest quality.
ABOVE: These settings result in fastest print at 300 dpi printer resolution. Good for a quick proof.
4/16/2007: Color, Color, Color...
Since color is so closely tied to image quality the quest for inks and papers that display the widest possible color gamut has been one of the main objectives in developing inkjet printers from the very beginning. In my discussions with HP engineers, which can be verified by the short video interview shot by Michael Reichmann that appears on his Luminous Landscape website, they are confident that the upper limits of the inkjet color gamut and image resolution have been achieved. That is to say, they believe it is unlikely that adding another ink to a 12-ink printing system will extend the gamut. While there may be differences in the hues certain printer manufacturers choose to favor, an extension in one area of the color gamut results in a loss in another, and which one is better is no longer a function of gamut size, but personal preference. With the HP Z3100 and any of its comparable competitors, printmakers have available the widest color gamut, highest resolution and therefore the best image quality that we are likely to see in inkjet printing for a long time.
So, with image quality virtually a moot point, on what playing field are these manufacturers going to compete? For us, the end-users, the outlook is rosy because what is left to attract our purchasing power are competitions in price, features, reliability and service. And, it is promised that with digital printing still on the increase, the competition between the major players will be stiff to say the least. Since it is one of the first of this new generation of inkjet printers to enter the field, a look at the Z3100 will give you a good snap shot of what this feature fever is likely to bring us.
In terms of features such as 44-inch printing widths, 12-ink color gamut, automatic printhead maintenance, gloss enhancer, on-the-fly gloss or matte black printing and copious amounts of easily accessible support and advise, one feature that gives the HP Z3100 engineers and marketers a lot of pride is the inclusion of an on-board spectrophotometer. The purpose of this mechanism, designed in conjunction with Gretag i1 Technology, is to allow the average digital printmaker to create their own custom color profiles for any paper they wish to use. Today so many paper manufactures, old and new, have seen the depth of the inkjet market that there is a huge and exploding supply of inkjet papers of all types and purposes. What the HP Z3100 spectrophotometer allows the printmaker to do is develop a custom, easily updatable profile for any of these papers.
However, in truth, I have never been a big believer in color profiles. Of course, I used them. You have to choose a color profile when you load any paper, but for some reason I found that I had to make some very controlled and targeted tweaks in the files I printed in order to get the results I want. A color profile was never enough and, over time, I began to write it off as a limitation that I had to live with printing on the CP2500. Finally, with the arrival of an ample range of matte fine art papers, Myriam and I are anxious to see how the spectrophotometer works and how an image would translate from one paper to another. The test group has been notified to start sending their art files and a new and colorful fever is upon us.
Part III coming soon...
To read Part I of this article, click here.
About the Author:
JD Jarvis is co-author of "Going Digital: The Practice and Vision of Digital Artists," Thomson Course Technology, published July, 2005. You may sample some of his art made digitally at www.dunkingbirdproductions.com. He can be reached at info@dunkingbirdproductions.com.
^ back to top
(back to Reviews index page)
Home | About Us | Advertise | Contact Us
News & Reviews | How-To's | Resources
© 2002-2007 Harald Johnson Communications. All rights reserved.
