Luminance Masks From Channels

[Mike4Life]

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.

 

[Lisbon]

Hi Mike.

I also use this technique, but with a slight difference.
Instead of creating a new alpha channel, I copy the channel to a new layer.
There are several ways to do this in Affinity Photo. One way is to right-click on the desired channel, eg "Background Red", and choose "Create Grayscale Layer".

But my preferred way is using procedural textures.
For example, to extract the red channel, you start by duplicating the background and the procedural texture would look like this.

After cleaning up your layer, you can right-click and convert it to a mask (Rasterize to mask).

Instead of Rasterize to Mask, you can also load the layer as a selection by pressing Ctrl+Alt+Left_Click on the layer containing the channel.

[smadell]

The attached video is a method that I use often. It works well, and is a nice way to deal with selections and masks involving intricate subjects (like leaves on a tree, wispy hair, and so forth). It doesn't involve using Refine Selection which works well when it works, but frequently causes other issues. Obviously many ways to skin a cat, but this is a tried and true method that works for me.

 

 

[firstdefence]

Another good video here: 

 

[Mike4Life]

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