Re: [Gimp-user] dilemma
On Sat, 2008-04-05 at 17:46 +0100, norman wrote: > < snip > > > > It sounds like some color management problem, but I'm not sure exactly > > what. To start, have you profiled your monitor? Are you choosing a > > profile in gimp? The image viewer almost certainly is not using any > > profile information except thaqt which may be loaded into the video card > > memory. Gimp may be doing something different. > > I have not profiled my monitor and I am not choosing any special profile > in GIMP. Is it complicated to profile a monitor? Profiling a monitor can be fairly complicated. You can find a general discussion of it at www.normankoren.com/color_management_2A.html. It involves two steps: calibrating the monitor thru hardware controls, and adjusting what is sent to the monitor from the RGB values in the image file, ie.e. the color balance of the image as it appears on the monitor. You can do a basic calibration by setting contrast and/or brightness (depending on whether the monitor is a CRT or LCD) and then setting gamma using images on Koren's web site. (See also www.cs.cmu.edu/~efros/java/gamma/gamma.html.) You can set the gamma under Linux using either xgamma or xcalib. The second part of the proces involves color profiling, for which you really need a device such as the Eye One Display or better the Eye One Pro. the latter is much more expensive but also allows you to profile your printer. Under Linux, you can both calibrate and profile your monitor with such a device using the program lprof or using the argyll suite of programs. The latter can also do your printer if you have the right device. Lprof may be already available as a package under ubuntu; it is under Fedora. The argyll suite must be donwloaded. The documentation is pretty clear, but it must be read very carefully, and you have to know what the words mean. It also has a very active users group which can be very helpful. Try googling "argyll color management" for more information, But I should warn you that the learning curve for these tools, and for color management in general is very steep. If you are determined to understand it, you should start with Norman Koren's web page, but you would be well advised to study a book like Real World Color Management. It covers the basics very well, but most of the book assumes you are using commercial software available under Windows or MacOS. Some of this can be adapted to Linux, but you it is hard to dig out just that part. I've been working on understanding color management for many months, and I don't think I've completely mastered it yet. Unfortunately, the gimp manual documentation on the subject is pretty sketchy and some of it, I think, is misleading. I suggested some improvements to the gimp-doc group, but the last time I looked, they had not been adopted. You should probably do a minimal adjustment for gamma, as described on Norman Koren's web page, but you will probably find it doesn't make much difference. The default calibration and profile---sRGB---is probably not that far from what careful profiling would yield. I suspect that this is not the problem in your case. As I suggested earlier, it sounds as if the image viewer and gimp are using different profiles or assuming different color space models, which amounts to the same thing. It is remotely possible that ubuntu has added some color profiling to its interface, but I really doubt that. Gimp will by default use sRGB, which is supposed to be an average profile for monitors, and the image viewer is probably also using it. If a profile for a color space is embedded in your image file, gimp may be choosing that instead, and then what it shows will be different from what the image viewer shows. You can check that by using Image properties>Color Management in gimp. Also, just what gimp will do with an embedded profile it finds in an image is determined under Preferences>Color Management. > > Norman > ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] dilemma
Hi norman, On Sun, Apr 6, 2008 at 8:13 PM, norman <[EMAIL PROTECTED]> wrote: > > > It sounds to me like norman does have color management, but his viewer > > either doesn't support it or color management info isn't being saved. > > To avoid these kind of problems, I convert the final image to the > > NativePC profile available at the following URL: > > http://www.aim-dtp.net/aim/download/aim_profiles.zip > > > > before trying to display it elsewhere. > > This ensures that it will display fairly normally even if there is > > some problem with color management. > > Thank you very much for trying to help me with my image viewing > problems. The more I read the more complex things appear to get but I am > learning. However, could I return to the examples which started this > thread. We have constants and variables. The constants, for me, are the > hardware and the images, the variables are the software. The images were > produced by my son, using his hardware running Ubuntu 7.10, and Bibble > Pro, from RAW images I supplied, and were made available to me in JPEG > without any image size reduction. > > I viewed these images using Eye of Gnome 2.20.1 (Image Viewer) which is > the default Ubuntu viewer, gThumb 2.10.6 and GIMP 2.4.2 with the > following results:- > > gThumb and GIMP produced, as far as I could see, the same image but Eye > of Gnome produced an image that I can only describe as having more > punch. In layman's language the colours were brighter and the detail > sharper. Maybe I am just expecting too much but then, unless my son and > I use the same software to prepare and view our images, how can we help > each other to improve our photography? Further points that might help: a) GThumb does not support color management, so what you see in GThumb should be typical of a non color managed display. b) GIMP has a correctly color managed display... providing you have the right profiles assigned. NativePC is a reasonable display profile to choose if you have no monitor-specific profile. If the image then does not display as you expect, then its profile is incorrect. Your RAW processing software should allow you to assign a profile to your image; GIMP also allows you to assign a profile and convert to a profile. Assigning a profile rather than converting to it can cause the types of discoloration you describe. Only assign a profile if you are sure that the image data is already in that format (eg. only assign a linear profile if the image data is already linear.) (however, if this were your problem, I expect you would notice it immediately... UNLESS, as Sven suggests, you may have colour management disabled. Check that it's enabled under View->Display Filters, and consider altering the relevant part of the preferences to 'color managed display' Hope that helps. ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] dilemma
On Sun, Apr 6, 2008 at 2:10 AM, Sven Neumann <[EMAIL PROTECTED]> wrote: > Hi, > > > On Sat, 2008-04-05 at 11:21 +0100, norman wrote: > > I have recently started comparing final images with my son where we both > > start with the same RAW image. He uses Bibble Pro only, whereas I have > > been using UFraw and GIMP. For some reason, which he cannot explain, he > > does not like my images mainly from the point of view of colour hence > > the comparisons. When I looked with Image Viewer, at the images he had > > produced, they were vibrant, sharp and had plenty of punch. However, the > > same images opened in GIMP, are washed out, not very sharp and lacking > > in punch. This caused me to look further and I found that this > > difference applied to all the images I have recently been working with, > > good in GIMP exaggerated in Image viewer. Good in Image Viewer, weak in > > GIMP. > > It's quite likely that the Image Viewer and GIMP are handling color > management differently. You should check if "Color Managed Display" is > enabled in the GIMP preferences and you can use the "Image Properties" > dialog to check if there's a color profile attached to your image. > > > Sven > It sounds to me like norman does have color management, but his viewer either doesn't support it or color management info isn't being saved. To avoid these kind of problems, I convert the final image to the NativePC profile available at the following URL: http://www.aim-dtp.net/aim/download/aim_profiles.zip before trying to display it elsewhere. This ensures that it will display fairly normally even if there is some problem with color management. (of course, it is better to make sure all your tools support color management. I haven't managed to do this yet.) ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] dilemma
Hi, On Sat, 2008-04-05 at 11:21 +0100, norman wrote: > I have recently started comparing final images with my son where we both > start with the same RAW image. He uses Bibble Pro only, whereas I have > been using UFraw and GIMP. For some reason, which he cannot explain, he > does not like my images mainly from the point of view of colour hence > the comparisons. When I looked with Image Viewer, at the images he had > produced, they were vibrant, sharp and had plenty of punch. However, the > same images opened in GIMP, are washed out, not very sharp and lacking > in punch. This caused me to look further and I found that this > difference applied to all the images I have recently been working with, > good in GIMP exaggerated in Image viewer. Good in Image Viewer, weak in > GIMP. It's quite likely that the Image Viewer and GIMP are handling color management differently. You should check if "Color Managed Display" is enabled in the GIMP preferences and you can use the "Image Properties" dialog to check if there's a color profile attached to your image. Sven ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] dilemma
Norman, did you use camera profile *.icc when processing RAW photos with UFRaw? If not, you photos *should* look slightly desaturated. norman wrote: > I have recently started comparing final images with my son where we both > start with the same RAW image. He uses Bibble Pro only, whereas I have > been using UFraw and GIMP. For some reason, which he cannot explain, he > does not like my images mainly from the point of view of colour hence > the comparisons. When I looked with Image Viewer, at the images he had > produced, they were vibrant, sharp and had plenty of punch. However, the > same images opened in GIMP, are washed out, not very sharp and lacking > in punch. This caused me to look further and I found that this > difference applied to all the images I have recently been working with, > good in GIMP exaggerated in Image viewer. Good in Image Viewer, weak in > GIMP. > > Could someone please explain what I should be doing to overcome this > dilemma? There must be some reason but, because of my lack of knowledge > of colour and its formation in terms of display on the monitor screen, I > have no idea where to start. We both use Ubuntu 7.10 and I use GIMP > 2.4.2. > > Norman > > > -- With respect Alexander Rabtchevich ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
