how can I apply image to a curves layer

[aham85]

I'm trying to accomplish a task I frequently use in PS where I open an image, add a curves adjustment, and then go to Image>Apply image, which then adds the background image to the curves mask in shades of grey and thereby allows you to adjust only the lights or darks of the background image via the curves layer. I have tried a few different methods, and nothing is working!

[thomaso]

Not sure what you want exactly – I guess the Blend Range Options can be a way to the desired result. With your adjustment layer selected click on the cog icon in the layers panel ...

https://affinity.help/photo/English.lproj/pages/Layers/layerBlendRanges.html

[smadell]

You seem to want to use a luminosity mask on your Curves layer. Blend Options is the way to go. Try these:

 

[Lisbon]

Hi aham85!

If you only need a grayscale version of the background (BG) then Ctrl+Alt on the BG thumbnail and add curves adjustment layer.

If you need a grayscale version of the visible layers then:

Method 1:
Merge visible (Ctrl+Alt+Shift+E)
Edit > Fill: Blend mode:Colour / Custom colour: H:0 S:0 L:Any value
Right click on the new layer and "Rasterize to mask"
Drag and drop the mask to the curves adjustment layer

Method 2:
Merge visible (Ctrl+Alt+Shift+E)
Ctrl+Alt over the thumbnail of the new layer
Add curves adjustment layer

Cheers.