DESC: At full power, it can be fired approximately 280 times. It charges in approximately 4 seconds and is more durable than you would expect. Guide Number 20 (ISO 100-m): The maximum Guide Number 20 When you are done shooting, you can rotate the shoe into the body. It's very convenient to carry around because it is so compact Compatible with TTL functions of digital SLR cameras: Compatible with the advanced flash output control function for Canon E-TTL II The latest high-accuracy TTL signals are recognized by just mounting this flash on a camera and turning it on.