The difference between a muddy result and a crisp, professional high key image comes down to one thing: precise exposure control. That means treating the subject and the background as two separate exposures, and measuring each one deliberately.

1. Expose the subject correctly first. Set your key light for a normal, well-exposed face. High key doesn't mean overexposing the person; skin tones and detail should hold up just as they would in any other portrait.

2. Light the background on its own. Use dedicated lights for the background and aim them evenly across it. To render as pure white, the background typically needs to sit somewhere around one to two stops brighter than your subject. Less than that and it stays grey; much more and the excess light starts bouncing back onto the subject.

3. Keep distance between subject and background. Giving your subject a few meters of space stops background light from spilling onto their shoulders and hair, and keeps the key light from greying the backdrop. It also gives you much more control over each exposure independently.

Quick Practical Tips

• Meter the subject and the background separately, ideally with a handheld light meter.
• Turn on your camera's highlight warning: the background should blink, the face should not.
• Watch the edges of your subject. Too much background light causes flare and eats into hair and shoulders.
• Flag the background lights so they don't shine straight into the lens.