How to key out a background when your subject is wearing the same colour
Tell Vizard Agent where the cutout is failing: an arm disappearing, a shirt going transparent. It looks at the matte itself rather than the finished composite to see the shape of the leak, shrinks the edge in stages so the hair survives the tightening, and keys only the region where the clothing and the background actually share a colour.
What do you type into Vizard Agent?
Say where, not just what. "The key is not clean" invites a global adjustment, which is exactly the move that trades the hair for the shirt. Naming the region, such as the elbow, the lower arm or the side of the torso, tells Vizard Agent the treatment should be local.
Prompt
What does Vizard Agent actually do?
The composite tells you something is wrong. The matte on its own tells you whether the leak is a thin halo, a soft area or a hole, and each needs a different amount of tightening. Then only the clashing region gets a fix. This was a composite where a child's shirt matched the background. In the session behind this article it:
- Removed the original background, checked the cutout's hair and body edges, and confirmed the file actually carried a transparency channel.
- Rebuilt the cutout with object segmentation to keep the hair and shoulders, verified the alpha and edge quality, and applied the segmentation matte as the alpha directly.
- Built the composite with the new background behind the subject and reviewed it for position and safe space.
- Looked at the matte itself to see the leak's pattern, then shrank the edge in two stages rather than one and rechecked.
- Isolated the arm and the side the review flagged and chose a key safe for that region, given the clothing and the skin.
- Composited with a localised mask rather than a hard box and checked there was no horizontal cut line where the local fix ended.
When does this not work well?
Some overlaps can't be separated. If the clothing is the exact background colour across a large area, or the lighting spills that colour onto the skin, no key distinguishes them and the honest answer is to reshoot or replace the garment. Soft or blurred edges vanish when shrunk, and low-resolution footage gives the matte too few pixels.
Common questions
Will the hair survive? That is what the staged shrink protects. Vizard Agent checks it.
Can it key just one part of the frame? Yes, and Vizard Agent feathers the boundary so it does not show.
Does it work without a proper screen? Often. Vizard Agent can segment the subject rather than key a colour.