First of all, thanks for your answer! Yes, it was the color the key of all. Once switched on white, it was exactly what I wanted. So for me it's now Ok.
Hubert, you have right, but I wanted to follow the tuto and was stuck with this color problem. thanks for your answers and help!
Goal was to use the pic adjusted into NIK Sharpener and reveal only the stone so retouched.
Thank you BOTH for taking time for me, that's so great such a responsiveness!
Cheers from Sweetzerland and MEB, here is the file.