B&W pixel image not working when used as a mask.

[JSS]

I have a stack of ~25 images of a waterfall in the woods.  I made pixel layers of the average and max images, which I blended for the water.  I use one image for the rest of the composition that I want to mask out the water to let the blended image through.  I created the mask by thresholding the blended waterfall, converting it to a pixel layer, and then adjusting it with the paintbrush.  The result is a B&W image - black on the waterfall and white everywhere else.  I drag the mask image over the icon on the "everywhere else" image.  The mask icon goes pure white, and it passes everything.  If I drag the mask out, it looks fine.  The Layers 1 screenshot shows Waterfall Mask, the everything else image, and the Avg + Max group.  Then I slide the mask image over the everything else image icon.  This creates an all-white mask.  Notice that the mask icon show the grey dot to indicate that it is a mask.  If I drag the mask image back out, it looks fine.  If I option-click on the mask icon to view the B&W image, in either of these two configurations, it looks fine.

What am I doing wrong?

Note:  If I create a mask on the image of everything else directly using the mask button and painting, it works.  But I wanted to use a threshold of the tree branches to get a better mask close in.

[Ldina]

@JSS Welcome! 

Try this...Adjust your B&W pixel Layer as desired (for masking purposes). It's still a pixel layer, not a mask per se. Right click on it and select Rasterize to Mask. This will convert your black and white pixels into a mask, which is essentially all alpha (degrees of transparency, from 0 to 100%). Then, you can leave it there in the layer stack, reposition it, or select Mask to Below to have it only affect that layer. You can also drag this "mask" layer onto another pixel layer, adjustment layer or live filter layer, and normally you want to drag a mask layer onto the layer thumbnail when masking. You can invert the mask at any time using Command+I on a Mac (Ctrl+I on Windows). You can also continue painting on the mask with black, gray or white to modify it..

Masking and alpha are different in Affinity products than they are in Adobe, and it's a different drill. I found it confusing at first...just a different way of working.

I hope I understood your request properly and that this helps.

[JSS]

That worked!  I figured I was doing something simple wrong.  The confusing thing was when I dragged the B&W over the thumbnail, it gave me the grey dot that suggested that act converted it to a mask.  However, as a mask, it only used the alpha channel, which is all white.

Thanks!

[Ldina]

You're welcome. I'm glad it worked!

[NotMyFault]

If you use a pixel layer as mask (in masking position), the alpha channel will be used, not the lightness values.