If the foreground is white and the background is black then the results will be different when you add the Gradient adjustment layer and you will need to do an additional step to get the correct ...

The black triangles mark the positions of the primary colors used to create the gradient. The white triangle marks the midpoint of the blend of the two primary colors. Give a suitable name to this ...

The two squares below the slider are gradient stops. The black stop signifies where the image is opaque and the white stop signifies where image is transparent. The Reverse Gradient button will ...