Calibrating white and black points

[psaccheri@gmail.com]

I have done new tests and found that writing the RGB values of my color card in the separate channels of the output slider in the Levels adjustment as you suggested gives me a correct calibration, my software shows approximately the same curve from GIMP and Photoshop. Hurray!

Hopefully I will solve the color space not embedded by my scanner the way the editing software expects it.

I hope GIMP will let us operate with 255 value even with images of more than 8 bit color depth.