What settings are you using that are coming out too bright? Are you, by any chance, using Auto ISO when taking those shots? If so, images will likely be to dark since the ISO is increased by the camera to expose well for the aperture and speed selected without regard to a flash mounted or not. Any light added at the time of exposure will cause the image to be over exposed. A good thing to remember is the metering in the camera is considering the light reflect now, not when the flash fires. One way to get around that is simply turn off Auto ISO or just switch to full manual exposure so you have control over how much of the exposure is from ambient light and how much is from the flash. By setting your exposure meter to show ambient lighting is going to leave the image 1 full tick under exposed according to the light meter at the bottom, the flash will supply the rest, about 1/2 the light needed for full exposure. Two tick marks under exposed on the meter will mean the flash will try to fill in 3/4 of the light for the full exposure.