set the black point/white and gray, help me?

[mantra]

Hi

i 'm used sometime to set the black point white and gray

for the gray , i add a gray layer , blend difference
after threshold and move the slider on the left (i guess it's right , move the slider on right sould be a mistake ,shouldn't ?)
and so i find the gray point

a question about the black and white point
i work only with photo
i guess the value 000000 for black an ffffff for white , are not natural

which values do you use ?

thanks
cheers

[mistermonday]

For RGB try 245 for white and 10 for black.
Regards, Murray