I probably should have pointed out that this picture came from a raw file. Because GIMP can NOT handle raw files it had to be developed using other software. In this case, that was Canon Digital Photo Professional (DPP). I was actually experimenting with the idea of using DPP to perform minimal processing necessary to produce a file that GIMP could open and then do much more refined editing.
One of my reasons for wanting to obtain raw files from the camera is the increased bit depth used to represent colors. A problem I've always recognized when doing this is that the camera can represent color with higher bit depth than the display devices that are used both for developing/editing the photo as well as the devices used by those viewing the resulting image files. The image files in this case are 16bit png format files.
However, keep in mind that all of the images included in my original post were obtained from the same computer/display and they are all from the very same GIMP edited image. How they could be so dramatically different is what I found surprising. I have been developing raw image files for some time now using various different programs for post-processing and have never seen anything like this before this.
With that said, I've now done a little more experimenting. I can now say that the difference in the on-screen appearance (again all with the same screen) varies according to what software is used to display the image files. For example, if I display both of the GIMP produced image files using the built in Windows (7) Photo Viewer the difference in appearance is sufficiently minor that it might go unnoticed. On the other hand if I use the Canon supplied My Image Garden program the difference is at least as dramatic as what I posted. Those screenshots, by the way, were from files displayed using XnView MP.
I think both My Image Garden and XnView MP are designed to handle 16bit format. However, I suspect I should consider myself lucky that Windows Photo Viewer is even able to display 16bit files. Might this help explain my findings?
Another finding that I suspect is relevant. I extracted the metadata from each of the 2 GIMP produced png files to text format using ExifTool and then compared them using Notepad++. The only relevant difference was in the ICC Profile. The first (really dark) one used something called "GIMP built-in Linear", which I've never heard of, whereas the second (lighter) one used what I'd have expected which is an ICC Profile called "GIMP built-in sRGB".
I think this may be a case where I wandered into a swamp without knowing what I was getting into. I somewhat recently started manually/consciously changing the precision to 32bit floating point when doing any kind of editing that might affect color rendering. The idea being to simply avoid the need for GIMP to constantly be doing back and forth conversions while editing with different tools. It seems that GIMP prefers the "Linear light" setting (which I never equated to an ICC Profile) and I had no reason to change it. In the past I think this got changed back to "Perceptual gamma (sRGB)" when I changed back to integer precision (either 8 or 16 bit) after being done editing. It looks like for some reason, that I cannot explain, that must NOT have happened in this case.
One of my reasons for wanting to obtain raw files from the camera is the increased bit depth used to represent colors. A problem I've always recognized when doing this is that the camera can represent color with higher bit depth than the display devices that are used both for developing/editing the photo as well as the devices used by those viewing the resulting image files. The image files in this case are 16bit png format files.
However, keep in mind that all of the images included in my original post were obtained from the same computer/display and they are all from the very same GIMP edited image. How they could be so dramatically different is what I found surprising. I have been developing raw image files for some time now using various different programs for post-processing and have never seen anything like this before this.
With that said, I've now done a little more experimenting. I can now say that the difference in the on-screen appearance (again all with the same screen) varies according to what software is used to display the image files. For example, if I display both of the GIMP produced image files using the built in Windows (7) Photo Viewer the difference in appearance is sufficiently minor that it might go unnoticed. On the other hand if I use the Canon supplied My Image Garden program the difference is at least as dramatic as what I posted. Those screenshots, by the way, were from files displayed using XnView MP.
I think both My Image Garden and XnView MP are designed to handle 16bit format. However, I suspect I should consider myself lucky that Windows Photo Viewer is even able to display 16bit files. Might this help explain my findings?
Another finding that I suspect is relevant. I extracted the metadata from each of the 2 GIMP produced png files to text format using ExifTool and then compared them using Notepad++. The only relevant difference was in the ICC Profile. The first (really dark) one used something called "GIMP built-in Linear", which I've never heard of, whereas the second (lighter) one used what I'd have expected which is an ICC Profile called "GIMP built-in sRGB".
I think this may be a case where I wandered into a swamp without knowing what I was getting into. I somewhat recently started manually/consciously changing the precision to 32bit floating point when doing any kind of editing that might affect color rendering. The idea being to simply avoid the need for GIMP to constantly be doing back and forth conversions while editing with different tools. It seems that GIMP prefers the "Linear light" setting (which I never equated to an ICC Profile) and I had no reason to change it. In the past I think this got changed back to "Perceptual gamma (sRGB)" when I changed back to integer precision (either 8 or 16 bit) after being done editing. It looks like for some reason, that I cannot explain, that must NOT have happened in this case.