What is alpha?

[Snowfish]

Hello. I see alpha used quite a lot in some tutorials I watched on youtube. I don’t really understand how it works and would like some help.

[Sandymoon]

Hi !
Alpha is the name of the transparent color in your artworks. Its the part where there is no colors.

For exemple, you can block the alpha part of a layer in krita, so when you paint, you can’t paint where there is no colors.

[Michelist]

Again, I’m too slow translating, but anyway:

What is Alpha? I’m not necessarily the great color expert, but to me alpha is the concept of NON-colorfulness, or translucency.
Alpha is, if we look at the color space RGB/A(lpha), the transparent part beside R(ed), G(reen) and B(lue), and you can do a lot with it, especially in the layer stack, but I’m not the right person to explain it. But look here:

Clipping Masks and Alpha Inheritance

Michelist

[Snowfish]

Thanks to both of you!
So alpha is the part where it’s transparent.
I think that clears some things up.

[AhabGreybeard]

‘Alpha’ is a measure of the opacity of a pixel.
If a pixel is totally opaque, it has an alpha value of 1.0, an alpha value of 0.0 is a totally transparent pixel. So, ‘looking through the layer’, downwards, you will see some of the underlying image layers, depending on the value of alpha for each pixel in the layer.

You can test this yourself by using the Colour Picker tool and the Tool Options docker, set to sample from the current layer, then paint with differing Opacity values and use the Colour Picker to sample the results:

I got careless with the Opacity slider and set it to 51 instead of 50.

[Mer23]

Clipping Masks: Alpha inheritance, Alpha Lock & Groups in Krita by Sergio TelleZ

Possibly the best visual explanation of alpha I have seen so far. Hope it helps.