When to use a colour key, and when not
A colour key measures how far each pixel is from the colour you picked, in a colour space built to match how different colours look. Anything within the tolerance goes; anything a little further is made partly transparent. It does not try to understand the subject, which is why it keeps thin lines, small text and the gaps in a lettering that a subject solve would round over.
It is the wrong tool when the background is a scene — a room, a street, leaves. Then there is no one colour to take away, and the guided selection on the front page, which fits colour models to your photograph, is the instrument to use.
- Shadows on the backdrop. A shadow is a darker version of the key colour. Raise the tolerance, or turn on “uneven background” so the key follows the light across the frame.
- Subject and backdrop the same colour. A red shirt on a red board has nothing to separate it. Keep it with the brush, or use the guided selection.
Questions
How do I remove a black background?
Press Black on the Cut panel. The key becomes near-black (the darkest few steps only), and every edge pixel is unmixed against black, which is what makes fire, sparks, smoke and glow on black come out as soft light rather than a dark fringe.
The backdrop has two colours. Can it remove both?
Yes. The eyedropper stays armed on this page: click the first colour, then the second, up to four. Shift-click a colour on the picture to take the nearest key colour out again.
It removed part of my subject that is the same colour.
The key starts on 'connected to the edge', so a matching colour enclosed by the subject should stay. If it touches the background it goes too: lower the tolerance, or paint it back with the keep brush on the Refine panel.
What is the difference from the white background page?
The keyer is the same. That page starts on pure white with no clicking; this one starts with the eyedropper so you can pick any colour, and it allows several.
Is anything downloaded or uploaded?
No. The colour key is code that came with the page, and the picture is read and written inside this tab.
Related
- Remove white backgroundA colour key on white with exact unmixing, so anti-aliased edges become soft transparency instead of a grey ring.
- Remove green screenA chroma key on the screen colour read from your photo, with spill suppression for the green that lands on the subject.
- Remove background from logoKeyed on the logo's own background colour, trimmed to the artwork, with a square canvas when you need one.
- Fix the edges of a cutoutOpen a transparent PNG someone else made and take its white halo, colour fringe or jagged edge away.
