>I have been out of active photography for some years now, I >have been asked to take some pictures this weekend for some >friends. The venue is a large hall, high ceilings, and low >ambient light. The couple will be dressed in their wedding >attire (white dress and Tux)etc. I will be using my D300 and >SB900. Any pointers to a successful shoot will be appreciated. >Diffusers, white balance etc. | am not a novice but health >problems have stepped in so any help would assist.
When you shoot in a large room with low ambient light, it is usually incandescent, and you usually do not have to do anything special about the white balance, because the flash will make the entire exposure on the subject. With the camera on Auto-WB, the background will be a little yellow, but that is usually fine, because that just gives the images warmth.
However, if the lights are fluorescent, sodium, or mercury, you will probably want to 'gel' the flash to make its light match.
The important thing is to shoot with the camera in Manual mode and the shutter set high enough to eliminate the ambient contribution on the subject, so the subject color balance will match the flash and be correct.
As a starting point, for large rooms I use ISO 400, 1/80th, and f/4.5. I also use a Gary Fong diffuser pointed up inside 20 feet and pointed directly at the subjects beyond 20 feet. Your range will be limited due to minimal ceiling bounce to under 30 feet.
You have to also watch out for overexposure. The dark backgrounds will make the flash power increase whenever the subject is not perfectly centered and occupying a large percentage of the frame. The black suit that the groom wears exacerbates the problem leading to blown faces for white skin. The problem is much less severe with dark skin. I always start with the flash compensation at -2/3 stop point when shooting in those conditions. Then, I check the histogram and readjust the FEC as needed.
Of course, when shooting the bride in her white dress, just the opposite problem will occur, if the dress occupies a large percentage of the frame. The flash will turn its power down and underexposure will result. This can usually be corrected in post processing (if shooting raw), so I usually don't worry about it unless it is severe. I check the histogram regularly to verify I'm not off by more than a stop and a half or so.
The FV-Lock function is also very important in large rooms, to minimize overexposure. Assuming you use a constant aperture lens, you can zoom in on the face of the subject, fire the FV-Lock, and zoom back out, recompose, and take the shot. This will make sure the flash is always set to the face of the subject rather than the background or clothing. But, you can't do this with a lens that changes its aperture as you zoom, or the wrong flash power may be locked.
Oh, and I forgot: Make sure the flash is in Regular TTL and not TTL-BL! The metering mode of the camera doesn't matter as long as the flash is in regular TTL. If you shoot in TTL-BL indoors in dim light with the camera in Manual mode, your images will usually be very dark.