Flash Exposure Based on experience, here are a few tips.   TTL Flash: Fill in Flash - The camera will most likely do a fair job. Portraits or People - Add 1 Stop to the flash, it will brighten up the faces. Manual or Auto flash: Fill in Flash - Subtract 1 Stop. Portraits or People - Add 1 Stop to the flash, it will brighten up the faces. Light box or reflector on your flash unit: Add 1-2 stops, you will have to decide which works best for your particular diffusion device. In general, TTL Flash and AutoFlash always seem to be a stop dark for some reason.  Add a stop for better results. Whenever possible (low white ceilings are good for this) use Bounce flash to diffuse the light.  You will have to position the flash head at an angle (kind of like playing pool) so that the subject is in the deflected light path.  Approximate is close enough.  Add a stop for this technique.