06-20-2021, 06:18 PM
Hello
I write some more details to get some more help on the behaviour of GIMP.
I scan test prints using a Canon Lide 400 scanner where I set output as TIF, 8 bit depth, no automatic editing, Adobe RGB as color matching.
I used GIMP and Photoshop to edit the same scanned image (a step tablet with different shades of color in each step).
Inside GIMP the scan strangely shows up as automatic sRGB so I convert it to Adobe RGB, (I set in Photoshop the same color space).
I use my Spydercheckr 24 Color Card, where I use Adobe RGB values of its patches to calibrate the image into GIMP using the Levels adjustment and the color pickers. Since in GIMP the Output Levels has only one value space for writing the highlight and one value space for the shadows, I use the average value of the three RGB values for each color patch, white and black.
In Photoshop I use the Curves command, with the color pickers (very similar to the Levels in GIMP) and there I can write the three RGB values for each patch, white and black.
I process the scanned and calibrated image through a software that gives me a correction curve, reading the different tones in the different steps.
I get two different curves from the software, the curve of the image edited with Photoshop is higher than the curve of the image edited with GIMP (the image edited with GIMP is lighter than the one edited with Photoshop, so it needs less correction).
Since the only difference is the software that I use and the calibration inside it, I wonder how GIMP makes that calibration compared to Photoshop. And if there is a different way I can calibrate using a color card inside GIMP.
If anybody can help me.
Thank you
Attached a superimposed image of the two curves for easier visualization and discussion.
I write some more details to get some more help on the behaviour of GIMP.
I scan test prints using a Canon Lide 400 scanner where I set output as TIF, 8 bit depth, no automatic editing, Adobe RGB as color matching.
I used GIMP and Photoshop to edit the same scanned image (a step tablet with different shades of color in each step).
Inside GIMP the scan strangely shows up as automatic sRGB so I convert it to Adobe RGB, (I set in Photoshop the same color space).
I use my Spydercheckr 24 Color Card, where I use Adobe RGB values of its patches to calibrate the image into GIMP using the Levels adjustment and the color pickers. Since in GIMP the Output Levels has only one value space for writing the highlight and one value space for the shadows, I use the average value of the three RGB values for each color patch, white and black.
In Photoshop I use the Curves command, with the color pickers (very similar to the Levels in GIMP) and there I can write the three RGB values for each patch, white and black.
I process the scanned and calibrated image through a software that gives me a correction curve, reading the different tones in the different steps.
I get two different curves from the software, the curve of the image edited with Photoshop is higher than the curve of the image edited with GIMP (the image edited with GIMP is lighter than the one edited with Photoshop, so it needs less correction).
Since the only difference is the software that I use and the calibration inside it, I wonder how GIMP makes that calibration compared to Photoshop. And if there is a different way I can calibrate using a color card inside GIMP.
If anybody can help me.
Thank you
Attached a superimposed image of the two curves for easier visualization and discussion.