I'm holding my VP-1 in my hands right now. Although it may not actually reduce the power by 5 stops, it is marked on the front of the dial from full to 1/32 power (-5 stops). If you are planning to use a Vivitar 283 with either a very modern film camera with advanced electronics or a digital camera, I would highly recommend using it with either a safe sync, or via the PC socket. Don't use it across the hot shoe because they're highly likely to put out way too much juice and fry the TTL circuitry at a minimum.