Sharpen does not work

[quand]

(09-20-2018, 08:17 PM)Ofnuts Wrote: Can you describe more in detail what you do, and what you mean by "does not seem to work"?

well, thanks for having paid attention

I'm really really not an expert and to make a picture more clear, I used under Gimp 9.x to put "radius " to zero, "amount" to a certain level and "threshold" to zero and I had a "good" result for me

here with same settings nothing occurs