Design Nomenclature / Digital Model Making
Alpha Channel
Also called alpha, transparency channel, matte
This entry has not been translated yet and is shown in English.
A per-pixel coverage value stored alongside colour, saying how much of the pixel the image occupies — not how see-through its colour is. That distinction decides compositing: premultiplied alpha stores colour already scaled by coverage and filters correctly; straight alpha keeps the two apart and needs care at every edge.
In practice
“Alpha” also names an opacity slider, a cutout mask, and in sculpting a grayscale brush stamp. Only the first of those is this.