I tested masking in the Blender compositor.
Please see the GIF below.
The 1st to 3rd outputs are Crptomattes(obj, mat, asset) and the 4th to 5th outputs are ID Masks(obj, mat). All mattes have border artifacts on the edges of those things.
The following shows border artifacts not only in black but also in normal color correction.
What did I miss?
How to use Cryptomatte or ID Mask correctly without border artifacts in Blender compositor?
I’ve attached a blend file to help you write your answer.
Compositor Spill.blend (158.7 KB)