[Luminance Masks From Channels]

Thanks so much for your responses. I will look into the videos and explanations you provided. 

[Luminance Masks From Channels]

Hello, and thank you for reading.

I've been a Photoshop CC user for a few years, mainly to do photobashing and concept art for video games. I recently switched to Affinity Photo and I love the software, but there are some techniques I wish I could carry over from Photoshop. One of these techniques consists in selecting a channel in the image, usually the one with more contrast, and then duplicate it to create a second alpha channel, and use it to extract certain elements on the photo, for example, this is useful for extracting dark hair on a clear background without the pain of selection and refinement. I have looked at online tutorials on how to do this in photo, but haven't been able to find such a technique. Any help or pointers would be more than appreciated.