When I used CC6 I would use the following steps to create a spot channel that would print white under the portion of the image I wanted to.
1) Click on Channels tab and create a new spot channel.
2) Command (Mac) + click on the layer I wanted to have white under (the section was surrounded by marching ants).
3) Used keyboard shortcut, usually Command + 7, to select the spot channel.
4) Shift + F5 to fill with Black.
5) Saved as a pdf and made sure Spot Channels was checked.
That was it and it worked every time. It would print a white layer behind the portion of the image I wanted it to.
Now, using PS 2021, when I follow those same steps it prints a different color entirely. For example, when I create the new spot channel the default color is magenta so I leave it that way. When I fill it in (step 4) it covers the area with red and it prints red! Have the steps changed in PS 2021 to add white behind a color?
AdChoices