I am trying to remove part of an image, but each time I add a mask, that mask is always semi transparent. Opacity and Fill settings for the brush I am using are set to 100% and blending modes are set to normal.
I have never come across this before and I think I have tried everything. I don't know if this is a Photoshop problem or if there is a setting I should change. Any idea what is it?
As sergeydyadyul suggests in the comments, please make sure that the colour you use to fill the black part of your mask is actually fully black. Not just CMYK 100%K black, a full
0,0,0 RGB black.
Especially with the colour picker, it's easy to accidentally select a very dark grey. Just drag the circle all the way beyond the edge of the picker to ensure a good black, or manually enter
#000000 in hex mode.