Developed specifically for Digital SLR cameras with the latest TTL flash control technology, the Nissin Di466 is a versatile unit featuring a guide number of 33 (m @ 100 ISO/). Flash exposure compensation is provided in 6 steps by half stop increments of -1.5 -1.0 -0.5 +0.5 +1.0 +1.5 by controlling a switch on the back panel. For ease and speed of use the batteries are held in a convenient battery cartridge where the battery contacts are all aligned in one direction. An all round fantastic third party flash unit!