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

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

On Sun, Apr 6, 2008 at 2:10 AM, Sven Neumann 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.)

Hi norman,

On Sun, Apr 6, 2008 at 8:13 PM, norman 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.

I am forwarding my reply to norman to the mailing list, because i missed the fact that he was replying privately (ie directly to me, not to the gimp-user mailing list at all). Please note, norman, that omitting parts of conversation is rather poor netiquette*; as you had not clearly indicated that you wanted to keep our talk off-list, I decided to reply in a way that includes the list. If you disagree, please let me know; otherwise, in future please send an instance of your replies to the mailing list ('reply to all' should achieve this.. it's normal to use 'reply to all' with mailing lists rather than just 'reply')

*replying privately results in a gap in the conversation on the mailing list, where.. when I reply... my reply and quotation of your message can be seen, but not your original reply, since you didn't send it to the list. the resultant conversation looks fragmented.

---------- Forwarded message ---------- From: David Gowers
Date: Sun, Apr 6, 2008 at 11:59 PM
Subject: Re: [Gimp-user] dilemma
To: norman

Hi norman,

On Sun, Apr 6, 2008 at 11:12 PM, norman wrote: > Once again, very many thanks indeed. For the record, the Display Filters > shows 'No filter selected' under the left hand column and Colour > Management ticked in the right hand column. In Colour Management in > Preferences, Mode of operation is set to 'Colour managed display' RGB > profile set to profile/None, Monitor profile I have set to nativePC. I > can still a differences between the images, those in Gimp lack a certain > crispness.
>
> The images used show the Colour space, in Image properties, as RGB > colour and a Colour Profile of sRGB IEC61966-2.1 with WhitePoint D65. (the same, for both his images and yours?)

So, what happens if you set your display profile to sRGB IEC61966-2.1 with WhitePoint D65?
Perhaps this is a better fit for your display than nativePC. Does that fix the viewing problem?

You might also consider checking out what the respective images look like when you disable color management completely, if the above does not help.

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