Using Channels to Create Selections/Masks

[philwizzer]

Hi

I'm  a little confused about the differences between Affinity and Photoshop in terms of copying a channel (e.g. red) and then using this to create a selection/mask that can be applied to an image?  The process seemed a little easier in PS or perhaps I was more familiar with it.  For example using the red channel to which a levels adjustment is applied to select bright hair against a dark background  in order to select?

 

Also what is the difference between the 'composite' red fore example and the 'background' red?

 

Thanks

[R C-R]

1 hour ago, philwizzer said:

Also what is the difference between the 'composite' red fore example and the 'background' red?

Composite refers to the cumulative channel contribution of every layer in the document. "Background" refers to the contribution of the currently selected layer with that name. If you renamed it from the default to something else, like "Photo" or "Layer one," then that name would be used instead when that layer is selected.