Most theatrical light bulbs or lamps are tungsten-halogen (or quartz-halogen). Which most consider is an improvement on the original incandescent types that used halogen gas instead of an inert gas. High Intensity Dis-Charge light bulbs (known as HID lamps) are common where a very intense bright light output is required, for example in large follow spots. For example a HMI type lighting (hydrargyrum-medium-arc-iodide) floods, and auto-mated fixtures use HID's. These types of lamps cannot be electrically dimmed. Some specially-designed fittings now use light emitting diodes (LED's) as a light source. LED's are ideal where an intense but unfocused light source is required.