Using my SB900 or my SB800's on camera in TTL-mode (FP but not BL) the resulting picture is well lit and exposed. If I use my SU800 to trigger the flash the pictures gets underexposed (same settings on camera and same distance to subject with flash on/off camera, i.e. manual mode, matrix metering, F7.1, S125. distance to object some 2 meters (6.5 feet), the SU800 set to commander mode and not close up mode). Is my SU800 faulty or is there something that I'm missing? There is no doubt that there is enough power to expose correctly (with EV compensation or the flash in manual mode) and I can't understand why the unit causes underexposure. Input is highly appreciated.