Curtain fabric offers varying levels of light transmission, with a closeness rating indicating its effectiveness. Fabrics with a rating of 9-10 provide significant light blocking, while sheer fabrics allow light to filter through. Blackout fabric stands out for its opaqueness, completely blocking light. Natural light interacts with window treatments, and factors like blinds, shutters, or curtains affect light control. Transmittance, reflectance, and absorbance determine how light passes through, reflects off, or is absorbed by a treatment. Curtain versatility allows for customization and style options, while room orientation, daylight intensity, and sun angle influence the amount and direction of light entering a space.