On Thursday 28 May 2009 08:30:29 am H.Lekin wrote: > Hello ! > > I joined this list to get some working-level advice on color management > issues. Hope, this is an appropriate place.
This might not be the best place for this. > > My background: About 5 weeks ago, I started playing with the > vector-graphics program Inkscape. I made a color drawing for my > brother's birthday, which I printed out (png) in a copy shop. On this > print, a blue gradient fill turned into a blue to dirty-green fill. > > As far as I understand, I have to transform the RGB color space into > CMYK to get a correct print file as well as being able to soft proof > what I am going to print. I installed ECI + Adobe ICC-Profiles and tried > the Separate plugin for The Gimp, PDF/X-3 from Scribus, and finally the > command-line utilities of Lcms. > > I don't really understand much of what I am doing, what I actually can > do, and how to bypass that the bloke in the copy shop hasn't heard of > color management yet + can't give me a printer profile. This is a big issue. The only way to "by pass" a print shop that does not understand color management is to use another print shop that does. Many print shops on the Internet understand CM so that is one possibility. And depending on where you live it should not be too difficult to find a local print shop that understands CM. For example, here in the US a "big box" store chain named Costco has an inexpensive printing service and their web site publishes the printer profiles for the printers in each store. Almost every city and larger town in the US has a Costco store. This is just an example but my main point is that it should not be difficult to find a print shop that you can work with. You just need to ask around. But the basic rule is if the print shop does not understand CM and color matters to you then find a print shop that does understand CM. Also most CM aware print shops will be happy to talk to you and guide you through their process. So once you find a good print shop don't be afraid to tell them that you are new to CM and that you could use a little help getting your stuff ready for them. In most cases they will have a set of fairly detailed instructions that are good enough that most CM noobs will be able to figure it out without needing to ask too many questions. > Also, some of my > experiments yield strange, unexpected results. Also why do you think the results are strange. Have you calibrated and profiled your monitor? Are you using a CM aware application to view the results? If not there is no way that you can be sure that what you are seeing on the monitor is even remotely close to what it should actually look like. I am not saying that it is not close only that there is no way to be sure. > > > I assume, the png I exported from Inkscape is based on sRGB color space. Why would you assume that? > I used Gimp to convert it into a tif, and if I then > > tifficc -oISOcoated.icc -t0 file.tif file-CMYK.tif > the lightness increases considerably and the greenish hue isn't as bad > as on the print but still visible (via IrfanView). The output-profile > name is NOT written to the file (hex editor checked). Actually you can check for an embedded profile in any recent version of GIMP or cinepaint. No need for a hex editor. > How can such a file be properly displayed? You need an app that is CM aware that handles CMYK images and you also need to have your monitor calibrated and profiled. You might try cinepaint or Krita. GIMP does not support CMYK images yet but probably will sometime soon. Scribus could also be used and there are also likely other ways to do this. Also if you know what color space the printer has then you can also use any of the above apps to create a soft proof that will actually come close to showing you what it will look like once it is printed. Of course this implies that you can get the correct profile for the printer and that your monitor is calibrated and profiled and so on. > How can it be further > transformed, e.g. to a specific printer profile? You should keep the image in it's native color space or your normal working color space and only do the output device specific transform when it is ready to go to the printer. The printer specific copy should be treated as a temporary file that will be discarded after it has been printed and you should always keep the original. I believe that GIMP, cinepaint and krita all have the ability to do the transform. > > If I use > tifficc -e -oISOcoated.icc -t0 file.tif file-eCMYK.tif > the result looks very much closer to the original RGB, just a little > less brilliant. > Is Embedding how things are supposed to be done? Always? > > How do I go on with the copy shop now? Is color management only > application based or do nowadays (Minolta 2xxx; sorry forgot) machines > somehow handle ISO profiles without further adjustment? Is it senseful > to make him find his printer profile? If so, i.e. if we have to set it > up, is the configuration usually done via the printer-driver interface > or via the application (Photoshop)? The common processes are that the print shop tells you they want the document/image in some standard color space like ISOcoated.icc because they calibrate all of their printers for it (probably the most common for offset printers). Or they want the document/image to have the color space(s) embedded and they will convert it to the printers color space during their printing process. Or the print shop will publish device specific profiles that they want the document/image to be in and they expect you to do the conversion (the last one is what Costco wants - probably the second most common approach). > > If I use the Scribus-PDF/X-3 variant, which saves the png and tif > intermediates, is an Acrobat Reader in the copy shop a sufficient > application for color-managed printing? This depends on the shop. If they don't understand CM then all bets are off. If they do understand CM and you have handled creating the PDF file correctly then they should be able to handle it correctly no need to worry about what software they will be using. > > Is ISOcoated_v2_eci to be preferred over ISOcoated (ECI, 2004), or do > you suggest a different profile for my hobby case? I don't understand what you are asking here. You need to use the profiles for the devices you are using but many users convert all of their input devices from the device color space to a generic working color space. Most color savvy users now days use a medium to wide gamut generic RGB color space for their working color space. This would include things like BetaRGB and ProPhotoRGB. This of course assumes that you have created custom profiles for your input devices (scanners and cameras) and that you have calibrated and profiled your displays and have valid profiles for your printers. > > > Thank you very much for your help > H.Lekin > > --------------------------------------------------------------------------- >--- Register Now for Creativity and Technology (CaT), June 3rd, NYC. CaT is > a gathering of tech-side developers & brand creativity professionals. Meet > the minds behind Google Creative Lab, Visual Complexity, Processing, & > iPhoneDevCamp as they present alongside digital heavyweights like Barbarian > Group, R/GA, & Big Spaceship. http://p.sf.net/sfu/creativitycat-com > _______________________________________________ > Lcms-user mailing list > Lcms-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/lcms-user ------------------------------------------------------------------------------ Register Now for Creativity and Technology (CaT), June 3rd, NYC. CaT is a gathering of tech-side developers & brand creativity professionals. Meet the minds behind Google Creative Lab, Visual Complexity, Processing, & iPhoneDevCamp as they present alongside digital heavyweights like Barbarian Group, R/GA, & Big Spaceship. http://p.sf.net/sfu/creativitycat-com _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
