Luminous Landscape Forum
Raw & Post Processing, Printing => Printing: Printers, Papers and Inks => Topic started by: Haraldo on January 09, 2007, 11:07:47 pm
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Last post of the day -- promise!
We were talking (who knows where now) about calibration, linearization, and all that stuff as it relates to the new HP Z printers and Epsons. Remember?
I was getting confused too, so here's the deal (from HP Engineering):
The new Zs both calibrate (maximum density or Dmax for each ink individually, minus GE) and linearize (linear response in colorimetric density as a function of input digital counts) whenever you want (this is rolled into the "calibration" function). As far as I know, Epson does not do this in the field (your printer in your place) but everyone assumes they do some form of both in the factory. The Zs also do this for each media individually, with different Dmax goals and for your current environmental conditions.
(so where's Canon in all this?)
Harald Johnson
author, "Mastering Digital Printing, Second Edition"
DP&I.com ( http://www.dpandi.com (http://www.dpandi.com) )
digital printing and imaging consultant
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In reality, not much different to what a (proper) RIP would do ... just automated. Epson's ColorBase normalizes the response for each paper. It's unclear whether the generated settings update the driver files, or the printer itself. Irrespective, it's useless with third-party papers as it has no data to normalize against.
Do you have to calibrate and re-profile after a head swap? I would imagine this would get pretty old fast in the busy environments these machines are destined/priced for.
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I was getting confused too, so here's the deal (from HP Engineering):
HP Engineering is totally confused as well then, and totally delusional too. Are you sure they knew they were talking to a knowledgeable person? This has all the characteristics of marketing crap.
Think about it:
1. There is no such thing as a spectrometer (or colorimeter) that can see craquelure, and overprint- or drying-artifacts, especially considering they don't allow enough drying time to begin with. And they don't print nearly enough patches to calibrate the Dmax.
2. What constitutes a "linear" response? (Think this one through really long please)
3. True profiling, especially for custom papers, would be profiling the CMYK output, not "colorcorrecting" the RGB input. At the very least it should include adjusting the graybalance.
(Not much use in calibrating the Dmax for primary colors, when combination colors leak off of the page because too much ink was sprayed).
The profiling option on the HP is useful, because it is highly automated and it ensures that the printer will behave consistent. For the average user, this is helpful. For most average printshops this is really helpful. But between "behaving consistent" and "producing a colormatch" there is an insurmountable void that even live humans have not been able to bridge, but oh sure, HP came down the mountain and have blessed humanity with its predictive spirit.
There's definitely room for completely automated color such as implemented in the HPs, especially considering the many printshops that are (still) completely oblivious to cm, and eventually the software will become increasingly smarter and will be able to automate more and more of the profiling process. But Dmax and linearization are not part of that process.
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... Do you have to calibrate and re-profile after a head swap? I would imagine this would get pretty old fast in the busy environments these machines are destined/priced for.
Yes, you're supposed to calibrate with any printhead change. You don't need to re-profile unless you want to. Calibration is 8-10 mins. Profiling is 15-20 mins. Automatic. Check your stocks!
Harald
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Well, who got out of the wrong side of the bed here? ;-)
1. There is no such thing as a spectrometer (or colorimeter) that can see craquelure, and overprint- or drying-artifacts, especially considering they don't allow enough drying time to begin with. And they don't print nearly enough patches to calibrate the Dmax.
Huh? You're losing me, dude. "craquelure"? Why would I expect to see that on a fresh print from an inkjet printer? And yes, you can adjust the drying time from printing to spectro scanning to whatever you want. 5 mins is the Auto default for busy people. Take a day, a week.
2. What constitutes a "linear" response? (Think this one through really long please)
A linear response is a linear response. 50% in, 50% out. No?
3. True profiling, especially for custom papers, would be profiling the CMYK output, not "colorcorrecting" the RGB input. At the very least it should include adjusting the graybalance.
(Not much use in calibrating the Dmax for primary colors, when combination colors leak off of the page because too much ink was sprayed).
It IS profiling the CMYK output. What else would it be?
Are we talking about the same subject?
Harald
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Yes, you're supposed to calibrate with any printhead change. You don't need to re-profile unless you want to. Calibration is 8-10 mins. Profiling is 15-20 mins. Automatic. Check your stocks!
[a href=\"index.php?act=findpost&pid=95029\"][{POST_SNAPBACK}][/a]
So if you calibrate with HP Glossy (or whatever) the calibration will apply to (say) Photo Rag? I'm just trying to get a handle on what the calibration actually does, and how it's different to per-media linearization.
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I'm just trying to get a handle on what the calibration actually does, and how it's different to per-media linearization.
[a href=\"index.php?act=findpost&pid=95032\"][{POST_SNAPBACK}][/a]
I think you'll find that calibration is media independent. It is calibrating the printer to a known standard (which would be why it only accepts HP Adv Gloss) so that when the printer driver asks for 10% black, 40% Magenta etc. the same amount of ink comes out regardless of which machine you print on. Profiling and calibration are different. Ideally, if you have two machines which have been calibrated to the same standard then the same paper profile should produce identical results on both printers.
Justin.
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So if you calibrate with HP Glossy (or whatever) the calibration will apply to (say) Photo Rag? I'm just trying to get a handle on what the calibration actually does, and how it's different to per-media linearization.
[a href=\"index.php?act=findpost&pid=95032\"][{POST_SNAPBACK}][/a]
I am just starting to use Epson's ColorBase. Just an FYI... ColorBase makes a seperate calibration for each of Epson's paper types. So, the whole process could be time consuming and require one ink change from Glossy to Matte. There a 9 paper choices, so you print and measure 9 charts (or just print the charts for papers you use). It seems that after you calibrate several "like" printers and profile just one of them, that you could then use the one profile on all the printers that have been calibrated (saving a lot of time, paper, and ink). Just thought this would be of interest in the this HP discussion.
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I think you'll find that calibration is media independent. It is calibrating the printer to a known standard (which would be why it only accepts HP Adv Gloss) so that when the printer driver asks for 10% black, 40% Magenta etc. the same amount of ink comes out regardless of which machine you print on.
[a href=\"index.php?act=findpost&pid=95040\"][{POST_SNAPBACK}][/a]
OK, now I understand. There must be a per-media linearization as well, namely to determine ink loading etc. Michael's first-look review seems to confuse calibration with linearization: "The process of creating a profile has two steps; calibration and profiling". Or is there separate printer calibration and media calibration?
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My guess was that:
- Calibration/linearization is the same thing: it is done on a paper whose characteristics are known, and the game is to figure out the amount of ink to inject through the head to reach targeted RGB values on that given paper. It should be an iterative process I would think.
It could be impacted by the head itself, by the temparature, by the humidity,...
- Profiling is about using a calibrated printer to print patches with known RGB values on an unknown paper you are trying to profile. The game is to inject known amounts of inks that would - as a result of the calibration - produced the desired color on the reference paper, and to measure the colors produced. The gap of RGB values between the reference paper and the paper to be profiled is what is captured in the profile.
I am not sure to understand the relevance of the CMYK model in this story, since I assume that the patches to be printed both for calibration and profiling are defined in RGB terms, I suspect that the spectrometer measures the patches in RGB values as well, and the inks used are not CMYK anyway.
Am I wrong somewhere?
Cheers,
Bernard
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Calibration usually means adjusting a device to a known state. For printing that usually means to linearise the separate primaries. With 12 ink tanks you can argue what primaries means in this case, but for all practical purposes it can be limited to CMYK output.
The calibration target image by HP in the review suggests it calibrates CMYK as well as LCMK. A graywedge gradient would be printed with a transition from LK to K by dithering. The output is affected by this dithering process...
Adjusting the printing head output to a known state would involve using a designated output paper type, apparently HP gloss.
The actual profiling of the device/paper combo is obviously independent of this calibration state, but IF you calibrate, it should be done BEFORE profiling, which, according to the review is done automatically in that order. When not using HP gloss, I don't know what the target values would be for the calibration process.
Now, the printer prints using a CMYK model with a graybalance and ink deposit based on the paper selected in the OS printer driver. A matte paper will involve less ink and a different graybalance than a glossy paper which will involve more ink.
This however, is usually the most control one can assert on the CMYK output, all other corrections are commonly done in the RGB realm. So you are actually creating an RGB to RGB transform, after which the printer driver and/or the printer do their RGB to CMYK/LCMK magic.
Whether the HP actually does CMYK profiling, I don't know, but the profile target shown in the review looks remarkably like an RGB target to me.
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Well, who got out of the wrong side of the bed here? ;-)
Huh? You're losing me, dude. "craquelure"? Why would I expect to see that on a fresh print from an inkjet printer?
Because the ink doesn't hold on the media. Plastic foils come to mind as the obvious example, the plastic coating on the glossy papers is actually pores so the ink can reach the absorbing layer. If the coating is not correctly pores, the ink will not stick to the surface correctly, and either the print head will run right through the previously deposited inkdroplets and cause smearing, or your print must dry really long and end up craquelured.
And yes, you can adjust the drying time from printing to spectro scanning to whatever you want. 5 mins is the Auto default for busy people. Take a day, a week.
OK, my apologies. I missed that from the review. The drying time remains very relevant for the reason mentioned above, but alsop because some of print colormatching really is a 10degr observer problem for which we don't know what the tolerances are. A proper white balance would be the prime example. Print a grayscale gradient of decent size, let it dry for a day. Then print the same grayscale gradient the next day and immediately compare.
If you don't see a difference, then everything is humpty dumpty, but if you do see a difference then the difference is likely less than 1 delta E... So perhaps HP is correct that the inks dry to within 1 deltaE in 5 minutes, but whether that is enough for the ones purposes remains an individual assesment.
A linear response is a linear response. 50% in, 50% out. No?
No, 50% of what compared to what?
It IS profiling the CMYK output. What else would it be?
It may be *calibrating* CMYK, but it doesn't appear to be *profiling* CMYK... The target in the review suggest an RGB profile.
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So if you calibrate with HP Glossy (or whatever) the calibration will apply to (say) Photo Rag? I'm just trying to get a handle on what the calibration actually does, and how it's different to per-media linearization.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=95032\")
I do not own this printer, but I like to consult manuals of interesting products:
the Z3100 User Guide reads that calibration(+profiling) should be done for every different paper not yet calibrated on the same set of printheads.
Furthermore there are automatic alerts reminding you whenever you need to perform color calibration and You can check the color calibration status of the currently loaded paper at any time by pressing the View loaded paper key on the front panel...
The manuals are downloadable from this link [a href=\"http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?lang=en&cc=us&taskId=101&prodClassId=-1&contentType=SupportManual&docIndexId=179166&prodTypeId=18972&prodSeriesId=3204970]HP z3100 Manuals[/url]
(Hope that's not a Manual error like the minimum roll width of 18" which have been stated and demostrated as a Manual and Spec error: in fact, as per other threads in this forum, the actual minimum for roll width should be the same as that one of sheets, i.e. = 8.3")
Hope this helps
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Can anyone please tell me, if , every printer need rip, or, HP Z3100, no going to neede it, at all.
Thank You
BlasR
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I do not own this printer, but I like to consult manuals of interesting products:
the Z3100 User Guide reads that calibration(+profiling) should be done for every different paper not yet calibrated on the same set of printheads.
Furthermore there are automatic alerts reminding you whenever you need to perform color calibration and You can check the color calibration status of the currently loaded paper at any time by pressing the View loaded paper key on the front panel...
The manuals are downloadable from this link HP z3100 Manuals (http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?lang=en&cc=us&taskId=101&prodClassId=-1&contentType=SupportManual&docIndexId=179166&prodTypeId=18972&prodSeriesId=3204970)
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Thanks for the link. So, from page 60 in the Z3100 User's Guide, changing a printhead will flag the calibration for each paper as "obsolete". Given a quoted average life of 2500ml for a printhead, and six printheads in the printer, you're up for a new calibration/profile roughly every 400ml of ink used (3 ink carts worth) ... and for every paper you use. Just as well it's automated! Of course, you could just continue to print with the old profile. There is no printer wide calibration.
Duh! It's 2500ml per printhead, not total throughput. This presumably totaled from just the two colours that feed a printhead. Given that some will get used more than others, and some will fail closer to the minimum warranty value, it's harder to predict when you're up for a new calibration/profile cycle. Maybe someone with a better background in statistics than me can tackle this! Regardless, it's an issue that we'll only hear about after the printers have been out there for a while.
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My guess was that:
..OMISSIS…
... I suspect that the spectrometer measures the patches in RGB values as well, and the inks used are not CMYK anyway.
Am I wrong somewhere?
Cheers,
Bernard
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=95049\")
…OMISSIS…
Whether the HP actually does CMYK profiling, I don't know, but the profile target shown in the review looks remarkably like an RGB target to me.
[a href=\"index.php?act=findpost&pid=95051\"][{POST_SNAPBACK}][/a]
Reading [a href=\"http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?lang=en&cc=us&taskId=101&prodClassId=-1&contentType=SupportManual&docIndexId=179166&prodTypeId=18972&prodSeriesId=3204970]The HP z3100 User Guide[/url] and based on my understanding, I think that Bernard explanation about calibration/profiling is quite correct.(for space seek, both Bernard's and Opgr's comments are excerpted, so see the complete originals clicking on the arrows on the right of the Quote)
Some specifics topics everybody can read by downloading the the Manuals (http://h20000.www2.hp.com/bizsupport/TechSupport/DocumentIndex.jsp?lang=en&cc=us&taskId=101&prodClassId=-1&contentType=SupportManual&docIndexId=179166&prodTypeId=18972&prodSeriesId=3204970):
-The profiles generated by the basic sw package (included with the printer) are RGB.
- Optionally you can buy the additional package “HP Advanced Profiling Solution” which allows you to profile also as CMYK in case of RIP
…The HP Advanced Profiling Solution lets you take control of your colors:
● Calibrate and profile all of your monitors—LCD, CRT, and laptop
● Automated RGB profiling via HP software drivers to ensure accurate printing (photos, designs, etc.)
● Automated CMYK profiling when your printer is driven by a Raster Image Processor (RIP) for
accurate digital prints and proofs
● Easily and visually edit your profiles for ultimate color control….
-The basic sw package (HP color Center) is operationally structured in three phases:
1-Paper Define
2-Calibration
3-Profiling
NOTE You can perform all three operations in sequence as shown, but you can also choose
to start with or stop after any of the three operations. With one exception:
color calibration is performed automatically after adding a new paper type…
-and about calibration vs profiling:
Calibration garantees consistency, while Profiling guarantees accuracy
…Color calibration provides consistent colors, but consistent colors are not necessarily accurate…
… From the measurements made by the spectrophotometer, the printer calculates the necessary
correction factors to apply for consistent color printing on that paper type.
It also calculates the maximum amount of each ink that can be applied to the paper…
Hope the above is useful and correct.
Ciao
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Thanks for the link. ...
...
...it's harder to predict when you're up for a new calibration/profile. Maybe someone with a better background in statistics than me can tackle this! Regardless, it's an issue that we'll only hear about after the printers have been out there for a while.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=95074\")
Stephen,
You are very welcome- glad to be useful once in a while
About printheads life, for those who have not read Michael's [a href=\"http://www.luminous-landscape.com/reviews/printers/HP-Z3100-review.shtml]review[/url]:
(enphasys's mine): the first one "13 cartridges"(divided may be by a number x? related to Failure Rate of the whole set of 6 heads) could be used as a starting estimated reference for how frequently I should re-calibrate because of printhead change, but only the future experience will tell the truth as both Stephen here above and Michael in his review say.
excerpt from Luminous Lanscape review (http://www.luminous-landscape.com/reviews/printers/HP-Z3100-review.shtml) of HP Z3100:
Of Print Heads and Calibration
.....The six heads in the Z3100 printer, at $69.95, each cost less than an ink cartridge, have a projected average life expectancy throughput of about 2,500 ML of ink, while being warranted for a minimum of 1000ML of ink. For the sake of argument, since the printers are so new and don't have a public track record yet, let's split the difference and rate the heads conservatively at 1,750 ML. Since each ink cartridge holds 130 ML of inks ($74.95), that means that on average one will have to replace each of the heads after about 13 cartridges of the same ink have been used. In other words, head costs add about $5 to the effective cost of each ink cartridge. This is essentially a trivial amount, and by way of comparison, far, far less than the cost of a single large sheet of fine art paper.
And, to save you the math, with these numbers it will only be after you have used some 156 ink cartridges of all colours before all six heads will have needed to be replaced – the equivalent of more than 4,000 large prints. This is several years worth of printing using a few hundred dollars worth of heads.
....
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Calibration garantees consistency, while Profiling guarantees accuracy
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Yes, I think this sums it up quite nicely.
Justin.
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Some further thoughts:
Maybe the printhead replacement and subsequent calibrations aren't that big a deal. For every paper you use, you'll do an initial calibration and build a profile. Then every time you want to do a run with that paper, you do a new calibration. This will correct for any earlier printhead change and also take into account environmentals. The profile you have may not be 100% accurate for soft-proofing but should give close to optimal results on the printer because the calibration is ensuring the best ink loading. Even with minimal (5 minute) dry-down, the relativity of one patch to another should stay about the same.
Looking however at the calibration, it appears pretty simplistic. When you're evaluating ink loading you can look at a number of factors: maximum density, differentiation between the 90% and 95% patches etc but also bleeding (how well fine detail holds up under that loading). There's also per-pass drydown to take account for. The optimal ink loading takes all these into account, but HP's calibration only appears to look at density. This is probably fine for most of their own papers, but people tend to put some oddball media through their printers and it will probably be inadequate here.
Another issue is the number of patches for the profile. At 473 (with the swatches at the top ... I counted them) it doesn't compare to the thrice-read 1728 patch targets I use for my Epson, but will require comparative testing to see how well it performs. HP enables more patches for more money (presumably which largely goes to GM/X-Rite as part of the deal) for those that think it's an issue. Or you could just use your own spectro and profiling software.
Note in the preceding that I haven't seen the printer, nor considering this in the short term (I already have something that works and the paper path of the HP is probably a show stopper for me) ... just ruminating on changes to the printing landscape.
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RE: "craquelure"
Because the ink doesn't hold on the media. Plastic foils come to mind as the obvious example, the plastic coating on the glossy papers is actually pores so the ink can reach the absorbing layer. If the coating is not correctly pores, the ink will not stick to the surface correctly, and either the print head will run right through the previously deposited inkdroplets and cause smearing, or your print must dry really long and end up craquelured.
I see where you're coming from, but this is not a situation most of us will encounter. I would venture that most here are printing on inkjet-receptor-coated media (or uncoated media but with known ink absorption qualities). I hope I never encounter the dreaded "craquelure" -- except in an 18th century painting!
No, 50% of what compared to what?
40%M input = 40%M on paper? Sorry, I'm not a linearization expert, but this has been my assumption in the past. As the HP engineer said, "linear response in colorimetric density as a function of input digital counts." That seems straightforward to me, but someone could probably explain it better. It's certainly not "marketing crap" as your hyperbole would suggest.
It may be *calibrating* CMYK, but it doesn't appear to be *profiling* CMYK... The target in the review suggest an RGB profile.
I think we're just using different words. The spectro scans the CMYK+++++ target patches to create the RGB profile (in the out-of-box version).
Harald
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Linearization corrects for out of linear response from the heads, ink, and paper. It may take a 30% signal to produce a 40% patch*. It is just another look up table, but a LUT that is normally built into the driver (but not always**). The end result is that a linear output (on paper) is obtained. The complete process would be like this:
send a 40% image, drive at 30%, receive a 40% print
Setting the ink limits by density only is not always the best method, but it is also highly dependent on the ink and paper. Sometimes you need to limit based on chroma, not density. Also since it is working both ink limit and linearization into a single step, papers that reach their limit very early will have a more course linearization correction curve. This is because there will be fewer steps making up that curve. If you have 50 steps in your linearity target (per channel), and you clip the ink limit at step 15, there are far fewer steps (15) than if you make the ink limit first, and then print that same 50 steps to get linearity (all 50 would be used).
* In reality, most of the Epson printers run with an inital ink limit (reduction) of around 60% maximum drive for inkjet coated materials. So what it really means is that an input of 40% is a drive of about 15% and a print of 40%. Uncoated materials and textiles may run right up to 100% drive, which produces ink running down your printer on almost all inkjet coated materials. Don't believe me? Get an Epson large format printer and a textile RIP and try it, the Evolution RIP springs to mind.
** In the upper level profiling packages, you can do a linearization step before creating the targets for the profile. When this is done the linearization measurements are applied to either the target, or the mathimatics involved in calculating the profile. You can also specify an ink limit (at least for CMYK and multi-channel profiles). I've done this with CMYK profiles when the RIP did not allow the system to be linearized (an old Fiery hardware RIP). Results can be night and day depending on the factors involved. Same can be said for proper ink limiting and linearization in a RIP that allows those variables to be adjusted. How the in profile linearization effects the profile differently from just a regular profile I don't really know, I just know that it does.
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I see where you're coming from, but this is not a situation most of us will encounter. I would venture that most here are printing on inkjet-receptor-coated media
Well, yeah, like I said, the HP offering will be really helpful in a lot of situations. I reckon it will cover 80% of the printing needs out there, say in the "good enough" color range. Although I do believe that the following scenario may not be uncommon: printshops will try to jam some of that heavy weight colorcopier paper used for greeting cards through the HP and I'd be surprised if something useful comes out the other end.
On the upside, maybe one of the manufacturers will recognize this market gap of a heavy weight double sided paper type that does allow inkjet greeting cards.
40%M input = 40%M on paper? Sorry, I'm not a linearization expert, but this has been my assumption in the past. As the HP engineer said, "linear response in colorimetric density as a function of input digital counts."
Conventional densitometry doesn't apply to inkjet printing at all. That is the entire core of the problem. Conventional densitometry requires 2 important ingredients:
1. Definition of a small range of most absorbing frequencies that will be taken as the reference (in reality a filter function over the entire frequency range is used),
2. Definition of the maximum absorption. (maxD).
Now, initially you would think that the maximum absorption is simply found at 100% ink deposit. You would be surprised in how many cases this is not true, even on matte papers. Even if this is the case, how does the printer know that the ink is behaving correctly? The most absorption may well occur while the ink is running...
Maybe HP has an additional test pattern like line-pairs that allows them to test this.
But the definition of the filter function also isn't as easy as it may seem. The maximum primaries of inkjets usually have a very different contorted behavior relative to the intermediated steps than for example press prints. Compare a decent Euroscale profile to any inkjet profile. This contortion is 3D through the colorcube, so testing for any combination of chroma and lightness will not mean anything.
So when you have some kind of definition of 1 and 2, you can end up with a definition of "linear", but the chances are pretty good that there is no relation to any visual linearity, and, more importantly, having "linearised" the primaries is absolutely no guarantee that the combination colors will suddenly behave properly, or predictably. This contrary to press printing, which is why they have gotten away with dot-gain control as the primary "color management" parameter for so long in that arena...
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"Calibration garantees consistency, while Profiling guarantees accuracy"
Yes, I think this sums it up quite nicely.
Justin.
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I agree, but for obvious reasons I would like to rephrase that to:
Calibration aims for consistency, while Profiling aims for accuracy.
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Linearization corrects for out of linear response from the heads, ink, and paper. It may take a 30% signal to produce a 40% patch*. It is just another look up table, but a LUT that is normally built into the driver (but not always**). The end result is that a linear output (on paper) is obtained. The complete process would be like this:
send a 40% image, drive at 30%, receive a 40% print
Setting the ink limits by density only is not always the best method, but it is also highly dependent on the ink and paper. Sometimes you need to limit based on chroma, not density. [...]
Interesting points. I found another HP tech document that explains how the Zs do this:
1. Density ramps are printed for each ink (x11, not GE) on the target medium.
2. The embedded spectrophotometer scans the chart with densitometry [note that it's a spectro so I suppose it could do chroma too]
3. Ink limits and input/output density relationships are computed for each ink.
4. A linearization table for each ink on that specific paper is computed.
This is not a driver function, and it's clearly customized for each ink and each paper. May not be perfect, but it seems pretty good for right out of the box and built into the printer.
Harald
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OK, well driver should maybe be a little more generic, it's putting the LUT inside the printer which is probably the best place to put it.
By doing the single pass limit/linearization they are betting that the papers that you use will not be too far off the norm. If you have one of these printers, and a spectro, you could try some Breathing Color matte polypro signage material http://www.breathingcolor.com/bc/catalog/index.php?cPath=505 (http://www.breathingcolor.com/bc/catalog/index.php?cPath=505) and see what happens. I find the chroma based limits to come in very soon and the density limits to go quite a bit farther. Most apparent on full cyan with my inks, the limit is something crazy like 50% after a 60% reduction. Most other materials go at around 75-90% for the Cyan after the same 60% initial reduction.
If you do try that polypro material, could you put it under hot running water for a while? Just curious how well the HP pigment inks do with water.
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This is a stupid question I'm sure - but why on earth would you ever want to put a work of art under hot running water?
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To see what happens when the sprinkler system at the gallery fails and douses your work . To see what happens in very humid environments . Because you are a sadist and just like to do things like this.
Yes I do use papers and inks that will survive a sprinkler malfunction. As long as the water coming out is clean, they will dry with no visible changes (just like a painting). To me this is important. If they don't dry completly flat, then you can steam press them back into shape
For signage on the material above, it is rated to be outdoor material, so it is all up to your inks when it rains. Most of the modern pigment inks should work on that material with minimum run off.
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[...]Yes I do use papers and inks that will survive a sprinkler malfunction. As long as the water coming out is clean, they will dry with no visible changes (just like a painting). To me this is important. [...]
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Not sure if the HP specs could satisfy all your requirements...
anyhow, for those interested,
HP Vivera pigment inks + some papers are rated as water resistant (by HP and/or [a href=\"http://www.wilhelm-research.com]WIR[/url]),
being "water resistant" defined by HP as:
" [...]HP uses ISO and internally developed tests and considers prints which pass the following tests to be water resistant : ISO standing water, water spray, water drip, and wet smudge. "
I have read the above from: http://www.hp.com/go/supplies/printpermanence (http://www.hp.com/go/supplies/printpermanence)