Optical pyrometers offer advantages such as non-contact measurement, making them suitable for high-temperature applications. They are also cheap, rugged, and have a wide bandwidth. However, they have significant disadvantages, including low sensitivity and poor time response. Additionally, the object being measured must be sufficiently hot to emit visible radiation, and systematic errors can arise due to emissivity differences between the pyrometer and the object. Overall, while optical pyrometers are useful in specific scenarios, their limitations must be carefully considered.