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Quality of large-format inkjet printing

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#1
Mike Parkes

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I've just had my first attempt at using a local print shop to print out a colour wall map from an online image (Patterson's Physical Map of N. America: http://www.shadedrel.../download.html) and I'm a little disappointed in the results. While the map still looks great and definitely wows the casual viewer, a close up look reveals the individual inkjet dots, lending the map a certain haziness (not in the original image) that obscures some of the detailed shaded relief.

A comparison with professionally published shaded relief maps (e.g. Government of Canada relief map) shows a definite difference in quality. My question is, is it too be expected that a colour inkjet (or laser) won't be able to match the quality of a professionally published map, or should I expect more from a print shop?

If the latter is the case, I'd appreciate any tips on what to look for in a local print shop with a large-format printer, given that it's not cheap to print maps of this size. Thanks in advance for any advice!

#2
Adam Wilbert

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Comparing a process that is geared to 1 off prints vs a process like offset printing that is used in 1000s of impressions isn't really fair. Offset will outshine an inkjet print any day. That said, it is possible for large format inkjet prints to look very very good. Its all about using high quality papers on a properly calibrated and maintained machine.

One thing to check into is how may colors the printer is using. Older inkjets just have 4 inks (CMYK). Some have 6 colors (they add Light Cyan and Light Magenta). The newer HP printers add 2 more blacks (Photo Black and a Gray) for a total of 8 different colors. More inks make for a larger printable gamut and smoother transitions.

Adam Wilbert
CartoGaia.com & AdamWilbert.com
Lynda.com author of "Up and Running with ArcGIS"


#3
Unit Seven

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The inkjets will have larger gamuts and therefore better overall colours than the offset but will generally not be as lightfast or as sharp as we are talking around a 720 dpi device resolution for the Epsons but your platesetter is going to be more along the lines of 2400+. The way inkjet dots are put down make this 720 better than the screened lpi that you get from your press so we are comparing apples with oranges a bit here but you font data will always look better on press.

As Adam said look for a newer machine which will have more inks—the new Epsons have 3 blacks (black, Light Black and Light Light Bleck) but this is only a real advantage for black and white photography.

Also I think if you are supplying postscript of pdf with font's included that the vendor has a postscript rip as this will render the fonts as the devices native resolution and not have them screened with the other fonts—this is the case for the files rendered on a press and am pretty sure large format postscript rips should operate the same.

Cheers,

Sam.
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#4
M.Denil

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The post above, from Sam Brown, displays a remarkable misunderstanding of the realities of print technologies. Remarks like "ink jets will have larger gamuts and therefore better overall colors than the offset" are simply and demonstratively untrue.

Inkjet color can simply never give as full a range of color as true half-tone process color.

The fact of the matter is that the widest possible print gamut is available to press printing (of whatever type: offset lithography, gravure, or whatever) because these processes use true subtractive color inks. Inkjet printers, by contrast, generally use a dye based toner that simply does not have the same light absorbing characteristics as do true inks. This is the reason that many ink jets today use 6 and 8 color systems: the colors placed on the paper cannot perform their task and need assistance, especially for light tones.

When printing on paper, the only light one can see is the light reflected from the surface of the paper. The best white paper reflects only about 80% of incident light, and every drop of ink on that paper absorbs some of that light, and so decreases the over all reflectance at that spot. True subtractive color ink (CMY) absorbs specific wavelengths of light:
cyan absorbs red and reflects everything except red light
Magenta absorbs green light and reflects everything else
yellow reflects all light except blue.

The same is true of blacks. True lithographic black absorbs all light (Okay, it is not a true black body by any stretch, but it is as black as it comes), ink jet black is just sort-of-blackish.

Inkjet dye based "inks", even when they are called Cyan, Magenta, Yellow, or Black. simply do not perform like that; they only emulate that activity. Sometimes one encounters pigment based "inks" for ink jet use. These color perform better (and are usually light fast longer) but they are still not true subtractive. A good demonstration of this is the ink jet's very poor performance in reproducing low percentage colors, like, say 2% - 5% process component colors. Modern ink jet fake these colors with 'light' color bottles.

Speaking of ink coverage percentages, this is another glaring misunderstanding in Mr Brown's post. He is confusing half-tone or mechanical screen resolution (line per inch, or lpi) with ink jet resolution (usually reported as dots per inch, or dpi).

Half-tone screens are for photos, and thus the dot sizes vary across the image, so I will discuss mechanical screens (used for solid patches of toned color) for simplicity. A mechanical screen lays down a regular, evenly spaced pattern of equal sized round (again, there are special screens, like the mezzo tint screen; but we are trying to be simple here) dots of color.

An ink jet cannot do this. An ink jet uses and 'ink jet' to spray ink at the paper. A high dpi, in this case, is good thing because the higher the dpi, the better an emulation of real litho screen dots is possible. The fact is, however, that a 720 dpi printer CANNOT recreate a good, full, round mechanical 100 lpi screen dot consistently across a page. If the ink jet cannot match press output at 100 lpi, it certainly cannot match it at 133 lpi, which is press industry standard screen resolution. (again, print tone screen, not computer screen)

Mr Brown wraps up with a completely mistaken understanding of why his text is coming off the press screened. It is MOST LIKELY NOT because of PostScript RIP and resident fonts!. The problem is much more likely that he has placed a raster layer above the vector (text is vector) layer. This will guarantee that every layer below the raster layer will also be rasterized. Mr Brown's explanation is pure moonshine.

Remember:
- rasters on the lowest layers! (I always flatten all the raster layers (including all the photos) into one layer before generating the press ready file: don't make the printing or PDF driver to deal with transparency).
- Vector layers on top of the rasters!
- Black stuff (including all black text) on top of everything! Set black to overprint!

- bonus tip: PDF's have unreliable color reproduction. Output for the press to an EPS if you want it to look like you expect.

It is unfortunate that there is so much misunderstanding and misinformation about printing rampant in the cartographic community. True information on these issues is readily available from the printing industry. I would suggest the purchase of the International Paper Company's little book called the Pocket Pal, for a good start.

I have worked with too many printers with distressingly low opinions of cartographers (and graphic designers, for that matter), but one has to agree with them when cartographers or designers expect the press to make perfect prints from dog's breakfast files.


Mark Denil
Washington, DC

#5
Matthew Hampton

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One of the biggest tips I can give is to use good quality paper. Maps on thick photo matte or gloss paper look remarkably better than plain bond. It costs a few more sheckles but if you are looking for good quality - use quality paper.

co-cartographic creator of boringmaps.com


#6
M.Denil

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One of the biggest tips I can give is to use good quality paper. Maps on thick photo matte or gloss paper look remarkably better than plain bond. It costs a few more sheckles but if you are looking for good quality - use quality paper.


Very true. A good paper will not only be whiter, and reflect more light (and your printed map is only reflected light), but it will also not allow the ink or dye-toner to soak in. Cheap, spongy bond paper soaks up ink, wasting whatever light absorbing qualities it has but also spreading into a larger area that you had planed. Small text characters become fuzzy blobs, hard edges get all funky, and other bad bad things.

A matte photo paper, or even better, an opaque mylar will have a hard, toothy surface that ink jets really like: the ink sits on the surface and stays where it was put. Of course, it takes longer to dry, and can be easily damaged when it is wet and soft.

#7
CHART

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May I suggest a bit more 'diplomacy' from Mark Denil.

I believe some on this forum have printed Tom Patterson's maps on Inkjet printers with success. Unfortunately, I could not find the links on this forum. (Hans...)

I would check the resolution of the file provided to your 'printer' along with its type (e.g. jpeg..).
Also find out the settings your supplier used to print your job. (e.g. was his plotter set to "best output").
Also find out if he manipulated the file before he printed it.

These information could help determine why your output was not as good as expected.

From an humble cartographer...
Chart

#8
woneil

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Although I've not yet produced much that involved any offset printing (and when I did the press preparation was all handled by the publisher) I have been finding the discussion of inkjet vs. offset very interesting. I've already ordered my copy of Pocket Pal.

In practice, my Epson Stylus Color 1280, with a nominal resolution of 1440 dpi, produces quite nice B+ size prints on high quality paper, and is claimed to have good fade resistance. And for A size, my new HP Color Laserjet CP2025dn does a remarkably good job. Although it's not quite photo quality in terms of density range, the results are notably crisp when printing flat color graphics. Great for producing small quantities of reports, which is what I bought it for.
Will O'Neil
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#9
M.Denil

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In the end, whatever the technology, if the results are what you want then things are good.

The trick is to compose to your output device. I have a color chart with lots of useful low percentage value colors and I print it on whatever output device I intend to use, and then pick my colors off that. That way, you know what a color will look like printed. Of course, you will have to resist the temptation to tweek the on screen color so it 'looks right' on the screen, because it is the printed color you really care about. A proof copy of the color chart from a print shop might have a small cost, but it can save expensive surprises later on.

Some years ago, I was running a lab with a number of large format ink jet plotters, the newest of which was an HP DJ5000, which did a pretty good job. In order to seed things up when I was faced with having to plot a couple hundred large format maps (for some conference), I also used our much older DJ2500CP (considered a good plotter in its day). I ended up making a completely new version of the map, with different colors, to get a close-enough match to the 5000's output. Of course, the 5000 spat out 5 or 6 copies for every one that came out of the 2500, but it took some of the load off the one plotter. I was able to use that incident to lobby to buy a second 5000.




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