Strange Result that might be related to Color Profiles

[ajax]

I originally thought this problem pertained to my printer and or related software.  However, after some experimentation I'm now thinking it is related to image editing which was done with GIMP.

In this case, I was editing a jpg file whose metadata did NOT include an ICC Profile.  When GIMP opened the file there was no mention of any ICC Profile.  The assigned color profile was the "GIMP built in sRGB" Profile which was no surprise.  However, when I went to print the edited version of the picture on my Canon Pixma Pro 100 photo printer the result was drastically different (extremely pale in one case) from what was expected.  I then went back and opened the saved .xcf file and performed an ICC profile conversion to a different profile that I normally use for the resulting image files from my photo editing.  That file printed as expected.

Unlike this situation most of my photo editing pertains to raw files from my own cameras (Note: raw files get developed using other software before being processed by GIMP).  This experience makes me think I need to gain a better understanding of the difference between Conversion and Assignment when it comes to color profiles.  I have reviewed the GIMP User Manual but I'm afraid it is no help when trying to understand what is going on in the scenario described herein.

[rich2005]

(05-22-2024, 04:03 PM)ajax Wrote: The assigned color profile was the "GIMP built in sRGB" Profile which was no surprise.  However, when I went to print the edited version of the picture on my Canon Pixma Pro 100 photo printer the result was drastically different (extremely pale in one case) from what was expected.  I then went back and opened the saved .xcf file and performed an ICC profile conversion to a different profile that I normally use for the resulting image files from my photo editing.  That file printed as expected.  

I can not explain that.  While the Gimp sRGB icc is basic it should not affect the printing. Just out of interest which icc do you normally use.

Quote:This experience makes me think I need to gain a better understanding of the difference between Conversion and Assignment when it comes to color profiles.  I have reviewed the GIMP User Manual but I'm afraid it is no help when trying to understand what is going on in the scenario described herein.  

This one a bit easier, you can check yourself using a sample point.  from left to right.
1. Image had all data removed and Gimp - built in - sRGB used when opened.
2. A new profile, AppleRGB, 'assigned'. The image is unaltered, pixel value remains the same. It is marked as out of gamut.
3. The AppleRGB used for 'converted'. This time the pixel values are changed.

   

[ajax]

Sorry about taking so long to respond but more pressing issues ended up needing priority.

The color (ICC) profile that I've been using for my photos once I'm finished editing comes from the Elle Stones collection.  Specifically the one named "sRGB-elle-V4-srgbtrc".  The basic reason for this preference is that I use different photo editing software for processing the image files and this choice allows me to end up with one consistent profile for many different pictures irrespective of what software was used to do the developing/editing.

I take the example offered by rich2005 to be consistent with my intuition.  That is to say "Assign" means to use the designated profile for the purpose of interpreting the data.  In that, the data is NOT changed.  On the other hand "Convert" means to make adjustments to the image data that reflect the difference between the current (assigned) profile and the designated new profile.

Most of my work developing/editing photos begins with raw files produced by my cameras.  Raw files do contain color profiles as it seems they should.  The experience to which this post pertains involves the editing with GIMP of jpg format image files that, I think, were produced by the camera.  They contain no metadata that defines a color (ICC) profile.  The metadata does designate a "Color Space" as "sRGB".  Might this mean that when GIMP opened those image files it "Assigned" the standard "GIMP built in sRGB" profile?  Most of the files I open with GIMP include color profiles and GIMP always asks if I want to keep that one or "Convert" to the standard "GIMP built in sRGB" profile. There was no ask in this case.

I think that cameras generally, maybe always, use (i.e., knows about) color profiles.  Why NOT include one of them when the camera produces an image file?

[Ofnuts]

(05-28-2024, 06:05 PM)ajax Wrote: Sorry about taking so long to respond but more pressing issues ended up needing priority.

The color (ICC) profile that I've been using for my photos once I'm finished editing comes from the Elle Stones collection.  Specifically the one named "sRGB-elle-V4-srgbtrc".  The basic reason for this preference is that I use different photo editing software for processing the image files and this choice allows me to end up with one consistent profile for many different pictures irrespective of what software was used to do the developing/editing.

I take the example offered by rich2005 to be consistent with my intuition.  That is to say "Assign" means to use the designated profile for the purpose of interpreting the data.  In that, the data is NOT changed.  On the other hand "Convert" means to make adjustments to the image data that reflect the difference between the current (assigned) profile and the designated new profile.

Most of my work developing/editing photos begins with raw files produced by my cameras.  Raw files do contain color profiles as it seems they should.  The experience to which this post pertains involves the editing with GIMP of jpg format image files that, I think, were produced by the camera.  They contain no metadata that defines a color (ICC) profile.  The metadata does designate a "Color Space" as "sRGB".  Might this mean that when GIMP opened those image files it "Assigned" the standard "GIMP built in sRGB" profile?  Most of the files I open with GIMP include color profiles and GIMP always asks if I want to keep that one or "Convert" to the standard "GIMP built in sRGB" profile.  There was no ask in this case.

I think that cameras generally, maybe always, use (i.e., knows about) color profiles.  Why NOT include one of them when the camera produces an image file?

My Canon 70D can be set to use sRGB or AdobeRGB color spaces for the JPG. Poring over the EXIF tags, it appears that there is a dedicated EXIF tag for this (0xa001 ColorSpace), but it only tells sRGB or AdobeRGB in practice so applications don't need to pull the profile data from the picture since there are only two choices and they can have these built-in.

[ajax]

Comments herein caused me to think that I needed  to confirm some of my assertions.  I have my cameras set to produce only raw files.  Therefore, I'm lacking both data and experience working with jpg files that are produced by cameras.  The jpg files I was able to check came from files obtained from others.

I also use Canon cameras.  One is the Canon EOS Rebel T8i (also called a 750D).  I went and changed the settings so as to produce both raw and jpg files and took an experimental photo.  The result shows that I was wrong when I said, "Raw files do contain color profiles ...".  At least for this experiment, there is NO "ICC Color Profile" included in the metadata for either the raw or jpg file.  On the other hand, there is an enormous amount of metadata lots of which pertains to color.

Looks like I need to further investigate the meaning and purpose of ICC Color Profiles.  However, I'm NOT optimistic that such will produce an explanation for the result that motivated this post.