“Chroma keying” is a common technique used in photography and filmmaking for replacing a background with another image. “Chroma” means colour, and “keying” is the process of removing that colour—usually green or blue.
These two colours are typically used because they don’t naturally appear in human skin tones or hair. This makes it easier to isolate the subject.
For chroma keying to work well, the background must be evenly lit with no shadows or bright spots. The subject should be far enough from the background to avoid green or blue colour spilling onto them. The edges of the subject must be in focus to ensure a clean removal.
If your photographer shoots the green or blue screen correctly, you may be able to replace the background yourself using free software tools. But if the background is poorly lit or the subject is contaminated with background colour spill, professional editing will be required.
Even with a perfect chroma key, your subject might still look out of place against the new background. Matching the lighting, colour tone, and depth of field is usually possible in post-production. But if the perspective is wrong, there’s no way to correct that convincingly. Perspective issues don’t apply to simple “flat” backgrounds.
More information on my photo retouching services.
