When fully closed, window shutters block out a surprisingly large amount of light. This is especially true for plantation shutters with large louvers. Shutters with wide slats are perfect if you want to flood a room with light when you open them during the day and excellent at blocking most light from entering when closed at night. As there are fewer slats in shutters with large louvers, there are fewer gaps through which light can pass. However, if you opt for shutters with small louvers, there are more gaps for light to penetrate, which reduces the shutter’s blackout capabilities.