The proper way to shoot a white background is to use four lights on the background and to have no more than 1/2 stop to 3/4 over the main light. To ensure you have a clean white without any flare from your background get your reading on the front subject and then read your white background and ensure it's no more than 3/4 over the front. Then turn your front light off and shoot an image with the subject. If you've lit the shot correctly you'll have a sharp silhouette for a clean, crisp look!
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