Sun 18-Nov-12 02:35 PM | edited Sun 18-Nov-12 02:48 PM by aolander
You don't want to "zero" the ambient light meter when shooting with flash. Even though the camera is in manual exposure mode, the flash will operate in TTL mode (unless you set it differently) and will correctly expose the subject. However, you can adjust the brightness/darkness of the background by selecting different aperture and/or shutter speed settings. If you want to expose the background one stop less than the flash exposure of the subject, adjust your settings until the meter shows underexposure by one stop. Usually, one would select an f/stop to shoot at, then adjust the shutter speed until you obtain the -1 stop. (You have to stay under the maximum sync speed, of course.)
The built-in flash on Nikon cameras operates in TTL-BL mode unless you use spot metering. I would recommend using spot metering in this case so you are in regular TTL mode.