An IR illuminator camera usually performs at its best when used indoors because it gives crisper videos. That is why the infrared illuminator systems can be found at hallways and rooms inside a building. The cameras that have infrared illuminators are used to improve an area's security. An IR illuminator camera usually performs at its best when used indoors because it gives crisper videos. That is why the infrared illuminator systems can be found at hallways and rooms inside a building. The cameras that have infrared illuminators are used to improve an area's security.