A traditional bulb type often found in older high-intensity discharge (HID) fixtures, these bulbs emit light with a blue/green tint. Use them to illuminate large outdoor areas, such as parking lots. Brightness is measured in lumens; the higher the lumens, the brighter the bulb. Color rendering index (CRI) is a measurement on a scale of 0-100 of how accurately the light from a bulb represents an object's true colors; the higher the number, the more natural the colors appear. Any CRI value over 80 will show colors true to life. A bulb’s estimated yearly cost is based on 3 hours of usage per day at $0.11 per kWh.