GN - Who Knew?
I stand on a Pelican 1620 case with my Nikon D300 camera, 18-200 lens, Manfrotto monopod, and Stroboframe flash bracket. For about 4 hours...and then I need medication. It is a simple recording of dancers on a plain black stage. The stage lighting is not so good as to permit ambient light photography so I use a couple of SB 700 flashes to illuminate them and stop action.
I use two flashes because the shooting is rapid and the batteries get hot. I rest one with the batteries out on the cold floor as I use the other one. There are 500 to 800 shots needed, so the batteries get a hammering.
I have taken to using one-shot AA lithium batteries for their capacity. But I always wanted to limit the amount of electricity going out with each shot to extend the life. Up until now I have left the SB700 flashes set at iTTL BL and been happy with the results, but idly searching through the internet...
I found a site that adequately explained the GN setting on the Nikon SB 700 flashes - and it seemed to just suit the situation I was going to be in. Once you set the flash on and click it down to the GN, the SB 700 extracts information thr0ugh the hot shoe as regards the ISO and aperture you are using. It tells you on the LCD screen the range of the flash. In my case it was 800ISO, f:8 and 37 -45 feet.
As I was fixed and the dancers were restricted to a stage at about the 40 foot mark, it all worked. the flash did not need to give out a pre-flash and then calculate the next move and the camera was never fooled by what refection came back from bright costume or dark stage. Each flash was consistent. It saved enough electricity to allow me to do the whole shoot on one set of lithiums.
Not a setting you could use every time, but a great resource for just this sort of situation. Yet another example of how good the SB 700 is!
Note: I have just about decided to get rechargeable NiMh batteries from here at the shop - they'll pay for themselves in 6 months.