This set consists of the powerful Nissin Di700A flash and the corresponding Air 1 NAS trigger. The Di700A has a guide number of 54. This is enough to bridge a focal length of 200 mm. If you do not want to set the flash manually, use the TTL measurement. With this accurate measurement you are assured of a balanced exposure. You place the flash on your hothsoe or operate it with the Air 1 trigger from a maximum distance of 50 meters. With the trigger you have full control over the flash and you control the flash power and the zoom range. The trigger has 3 channels with 8 groups each. This allows you to operate up to 24 flash units at the same time.