I use layers and masks for many images. I want to have a large image of the mask that I am using/creating so that I can see areas that I need to fix with my brush. The default size of the mask is too small to see if I have missed some spots. How do I make a big mask display?
If you hold the alt key & click. the mask, it will display larger in the image area as black and white, which you can edit. To get back to the image hold alt & click the mask icon again. Alternately if you go to the channel window & click the eye next to the mask Alpha channel, the mask will display as a red overlay on your image. The first option is better for editing the mask.. Hope that helps