On Monday 20 June 2005 09:50 am, Jan-Peter Homann wrote: > Hello list (cc. Wolf Faust) > If some people have succes by profilinig their printer via scanners. > We should get even better results, if somebody produce an additional > IT-8 chart as inkjet-print, measure this with a spectrophotometer and > sells this chart incl. characterization-data like a photographic IT-8 > chart incl. the measurement-data. > > A user who buys this chart inkl. data makes a special scanner-profile > only for reprofiling his printer. > > This would make only sense for pigmented ink, because prints of dye-inks > have to heavy colordrifts over the time. > > Wolf, if some people would be interested on such thinks, would you like > to distribute also such charts additional to your photographic produced > charts ? > > :-) Jan-Peter >
The problem is that there would have to be IT8.7 charts make for each specific ink being used. Since there are many pigmented inks being used this would result in a large number of possibilities. I think that the resulting charts would be very specialized and expensive. Currently I can get standard 5x7 Wolf Faust charts for $15 each. These have a useful life of about 2 to 3 years. If charts were offered printed in MediaStreet Enhanced Generations gen 6 inks (the ink I currently use) I would expect these to be significantly more expensive - on the order of $75 per chart perhaps more. On the other hand these might have a longer useful life than the current charts since the ink is rated for almost 200 years on some papers. Having ink specific IT8.7 charts would make the creation of printer profiles using a scanner significantly more accurate then when using generic IT8.7 charts since this would eliminate the metamerism problem. I would also expect it to be easier to get good results. This is because the IT8.7target and the printer target would both shift in nearly the same way in response to a given light source (it might also be influenced by the papers used in both targets) and the resulting profiles could be nearly as good as those created with a spectrophotometer. Would I pay $75 for an IT8.7 chart printed with the inks I use? Perhaps since I understand the implications of this. But many using scanner based profiling software might not understand how this would give them better results and many might be reluctant to spend that much more for something that they do not understand. On the other hand the profiles I am now getting using a standard Wolf Faust IT8.7 chart and an LED based scanner give me better output with my 3rd party inks and papers than the canned profiles Epson ships with the printer using the specified Epson inks and papers. The difference is not huge but it is there none the less. I should add though that it has taken me a lot of effort to get to this point and the learning curve is a steep one. Would a ink specific IT8.7 chart be enough better to justify the extra cost? The only way to know for sure would be to give it a try. Since these charts do not currently exist there is no way to test this. I also agree with Jan-Peter that this only makes sense for pigment inks. First because these inks exhibit very stable colors after the inks are dry (say after 24 to 48 hours) and because pigment inks exhibit much higher levels of metamerism than do dye based inks. It also appears that printer manufacturers are moving away from dye inks to pigment inks. For example all of the newer Epson printers are using pigment type inks where as a few years ago most of the Epson printers were using dye inks. > Bob Friesenhahn schrieb: > > profiling printer with a profiled scanner > > > > This is indeed an interesting issue. At first glance it seemed like > > nonsense to me, but after some more thought it seems that if the color > > of the LEDs are indeed narrow-band light sources and their colors > > happen to be located close to standard primary colors, then it should be > > possible to capture a nice scan. > > > > Using primary-color light sources may not solve metamerism though since > > there is still the sensor and the properties of what is being scanned to > > consider. This of course is true. My point was not that this would totally eliminate metamerism but rather that total metamerism effects would be reduced to low enough levels that it becomes a minor rather than a major problem. I have seen this first hand in my own digital darkroom and many of those that post to the ProfilePrism mailing list report the same thing. The author of ProfilePrism also uses LED based scanners to the exclusion of others for doing his own profiles. The real issue is not that the targets color shift in the scanner but rather that the printer target and the IT8.7 target tend to color shift in different directions and by different amounts. If a different scanner light source like LEDs results in smaller shifts or reduces the difference in the shift direction in both targets you have an improvement in the profiles that are created. Which of these are improved by using an LED based scanner I do not know but my gut feeling is that it is both. The point is that if both targets sifted by the same amount and in the same direction you would get nearly perfect profiles even if the amount of color sift was large. That is why Jan-Peter's idea of having ink specific IT8.7 targets is appealing. This would result in both targets responding to the scanner light source in nearly the exact same way. This would make the scanner light source much less critical and open up the possibility for more users to create high quality printer profiles without the need for very expensive equipment. ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
