The Interfit EXD400 Digital Flash Head (110V AC) is another step forward in the evolution of the EX flash system. The lightweight, economical monolight gives you a total of 400W/s of power, with precise power adjustment in 1/10 f-stop increments and a 6 f-stop range, providing excellent control over your lighting. Fan-cooling extends the life of both the 100W modeling light and the user-replaceable flash tube. A built-in slave cell responds to flash or to the optional infrared transmitter, and audible and visible signals alert you when the flash is fully recycled. It even has a program that overcomes the problem of pre-exposure flash from a camera setting off your flashes prematurely. The EXD400’s Auto-Dump feature discharges extra power in the capacitors, the second you turn down the power. The EXD400 comes with an umbrella reflector, built-in ergonomic handle and a flash tube transport cover.