How to work with Alpha Channels in Affinity Photo?

[MartinK]

Hello,

 

here is a connoisseur / expert, how to work with alpha channels in Photoshop, in order - in this case - to free branches or tree crowns. But I do not know how to proceed with Affinity Photo. The point channel calculations as in PS is not available in AP, but under "Channels" the point "background" for red, green and blue. Also one can create in AP a reserve channel - am I right in assuming that this is analogous to the copy of a mask channel, as it was made in the video?

 

Regards,

 

Martin