I received a call last week from Bank of the West in San Francisco, CA. The director of communication needed a portrait of one of his bankers with a client for their annual report. The photograph was to be taken at the clients location in Westminster, Colorado.
I was provide a sample photo that was taken by another photographer in another city to match the lighting on the subjects. The background in the sample photo was not a true white, rather a dull gray... poor execution in my mind.
We arrived at our location and found the conference room filled with a large table and about 20 chairs. We spent about 5 minutes pulling chair out and placing them in the hall way and pushing the large table to one side.
We put up a 9 foot white seamless for the background which fit right up to the conference table. I used the surface of the conference table to position one of my background lights. We used a total of 3 SB-800's fired via CLS from the commander unit built in on my Nikon D700. I used two SB's for the background illumination. Both strobes where mounted on Justin Clamps, one strobe placed on the conference table and the other on the window ledge.
Both of the background strobes where set to 1/4 power group B. You can see my foam gobo's placed on the head of both strobes, these are used to prevent light spilling on my subjects. The key light was also an SB-800 on a Justin Clamp and place on the back of a large Octa box. This strobe was set to 1/2 power and was placed in Group A.
I was able to use two groups on the CLS system for this lighting set up. The two strobes lighting the background are a "matched" set. Both strobes required the same amount of power out of each strobe and therefore could be place in the same group. With the CLS system, all strobes placed within the same group, in this case group B, each of those strobes receive the same power that the command unit is set for in that group.
On both my D300 and D700 cameras, the built in command unit will only control two groups, A & B. If I needed a third group C to light the shot, I would have to use an SU-800 command unit or another SB-800 as the commander.
In order to get a clean white for easy knock outs, your background needs to be about a stop and a half brighter than the key light on the subject.
You can see here with the background lights turned off we had sunlight driving through the blinds and projecting the window on the seamless. I was able to even out the light with the power settings on the background lights. Here is what the final image looks like.