On Friday 29 May 2009 05:09:44 am H.Lekin wrote: > On 28.05.2009 23:40, Hal V. Engel wrote: > > 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. > > Thanks a lot for the detailed reply. > > All my color-managed software uses the Lcms library. This is why I > skipped the GUIs for the programmer's CLI utilities. For any detailed > information on how they work, this must be the best place...?
I suspected that and as you can see from my reply I suggested some ways to do these things that are more "user friendly". A few years ago linux/unix users had to use the CLI utilities to do these things but now days there are end user GUI tools that make this stuff simpler and more accessible. The hard part for end users is getting an understanding of how this is supposed to work and how all of the pieces fit together. There is a significant learning curve for everyone when they start down that path. snip > I use this copy(!) shop for years; very friendly and helpful people. I > usually do my hard copies there. It was actually the first time that I > came round with a file to use their color printer. Discussing the colors > of the print, he asked me to bring a CMYK file. After I read through > program documentation and quite some articles, I asked for the printer > profile. This was as new to him as it was to me, but we are willing to > get in to it. Some printer vendors supply color profiles for their printers and if these profiles are used with the software that the vendor used to create these profiles they can give very good results. For example Epson has profiles that can be downloaded from their web site for various printers/papers. These also include documentation on how to correctly use them (IE. driver settings..). If the shop is printing using a Windows or Mac based work flow then the printer vendor may have good profiles available. But keep in mind that this needs to be a close match to the actual work flow that will be used. Also many paper and ink vendors do the same thing now days. > > I think, there is also a print shop in town, but I am not sure whether > they will be happy to do a single color print for me every now and then. You are correct about offset printing. They are not very likely to want to do single page jobs. Too much set up cost. In addition the result are generally not as good as you will get using other printing methods. What you need to look for is a shop that does photo printing where single page print jobs are the norm. These shops will generally use ink jet or dye sublimation printers where running a single page is easy. > > >> 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 used the ECI monitor test to adjust my monitor. I don't want to become > a professional, I just dislike that on my print blue turns into green > and wish to overcome this lack of understanding. Again my point is that unless you actually use some kind of objective method to calibrate and profile your monitor you really do not know what you are looking at. It might be close or it might not be. It used to be expensive to do this as the equipment was intended for graphics professionals in part because the companies that sold this stuff thought that this was the only market segment that existed. But the cost of the hardware has dropped dramatically in recent years as the manufacturers have found that there is a non-professional market segment for this and are now producing this stuff in much larger volumes. You can get Huey color meters with basic software for around $50. Is this as good as more expensive "professional" hardware/software? No but it is surprisingly good considering the low cost and will come close enough under most circumstance that it is hard to tell the difference with out very expensive equipment to check the results. > > In the viewing application, IrfanView, CM can be checked in the > settings. It also lists the name of the embedded profile. >From the net in the InrfanView forums: "Actually, neither FastStore, nor XnView, nor IrfanView are properly color- managed. They all pretend to be but really are not as they don't support monitor profiles and only convert images to sRGB, moreover at an enormous performance expense. Images won't display correctly if you happen to have a profiled display (most new computers, especially laptops, comes with a custom display profile nowadays)." > > >> I assume, the png I exported from Inkscape is based on sRGB color space. > > > > Why would you assume that? > > Well, I had to start somewhere and I think it was the best guess: > > I made a drawing with the vector-graphics program Inkscape. The copy > shop asked me to convert the Inkscape svg to jpg, png, tif or pdf. The > png I can export from Inkscape has definitely no color profile included. > As the print looks bad, the png is not in CMYK color space. For a color > space transformation, I have to set an input profile and tifficc > defaults to sRGB. What else should I have done? This is an issue and Inkscape does not appear to be color management aware. In this case Inkscape is effectively working in your monitors native color space and because you have not characterized it you don't know what the color space of the resulting image is. > > > Actually you can check for an embedded profile in any recent version of > > GIMP or cinepaint. No need for a hex editor. > > I used a hex editor as I couldn't rely on anything. If I open the tif > file with the embedded ISOcoated profile with Gimp, Yes GIMP does not handle CMYK images. That is a given at this time. > a message window > pops up saying that this file contains the embedded color profile sRGB > and whether I want to convert it to the standard RGB working space. If I > choose to keep the embedded profile, Gimp insists on sRGB built-in and > displays the image with great intensity (overcolored). > > On the other hand, Gimp's Separate plugin offers to keep the correct > profile as source color space. The main disadvantage of this plugin is > the lack of any tif compression, i.e. huge output files. In general if you are using GIMP you should not use a CMYK working color space. In fact for most users CMYK is a poor choice even if they are not using GIMP unless they have very specific reasons for doing this and I don't think your use case is one of those. > > > 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. > > As there is no printer profile available presently, and also because I > may have to use an other printer, I decided to transform to a standard > CMYK profile. Fist, to give me an impression of what my work will look > like printed, and second, I thought that a standard CMYK color profile > can be transformed to a specific machine color profile without a greater > shift in color properties. Are these good assumptions? These are not good assumptions. Unless you are using a properly characterized (meaning you have a good profile) display device with CM aware software that is properly setup there is no way to be sure that what you are seeing is close to correct. In addition, any color transform has the potential to cause significant differences in the output even a CMYK to CMYK transform since these color spaces can have significantly different characteristics (white point, gamut, black level....) and there are different rendering intents that can be used. > > I want to do my part of what there has to be done before I go to the > copy shop next time. Either I am happy with a straight print, or we have > to find the machine profile and transform into it. Are these assumptions > OK too? Perhaps since at least one of these is subjective (..I am happy...). It appears that the real question you are asking is "What do I need to do to be happy with the resulting print?" and that is clearly subjective. I don't think anyone can answer that question. But we can point out how color management works and if you apply those principles perhaps in the end you will be happy with the results. > > All I want is the blue not turning into green or other oddities. There > is no need for colorimeter-precise colors. And this is precisely what color management is intended to address. Even using measurement equipment it can be difficult to prevent oddities from showing up. The objective of color management is to keep those oddities small enough that they are not easy to spot. snip > OK, you always [have to] embed a profile. In the beginning, I didn't use > -e and even the soft proofs looked greenish. I thought that you do not > have to embed the profile - read s.th. about tagging - if it is > available on the system. This is not true? Most software requires that the profile be embedded otherwise it does not know how to do the transform. Some GUI software allows users to select a "from" and "to" color space when it does the transform. But the more normal process is to embed the "from" profile and then transform that into the desired color space. > > Is the command line above sufficient for what I want to do? What about > 'precalculates transform' or 'black point compensation'? > > How do you use the -p option 'soft proof profile'? I transform the color > profile and view the resulting file in a CM capable viewer. I consider > this being my soft proof, right? > > Is there any FAQ for beginners? I would recommend http://www.normankoren.com/color_management.html as a starting point. It has tons of information about CM including lots of details that are well beyond the beginner level yet it is accessible enough for noobs. But keep in mind that there is a significant learning curve. Also it is Windows centric so *nix users will need to read between the lines. snip > > My input device is a vector-graphics program; no scanner, no camera. Yes Inkscape which is not CM aware. Therefore your "input device" is working in the same color space as your monitor. But you don't know what that is. > > > This e-mail became really messy. It might be better to break topics into > pieces and start new threads... > > Thanks a lot 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
