Look at the picture of Sam here, shot last night with the Nikon D4, using a single flash aimed straight at him:
Not bad. Yes, as you all know, direct unmodified flash can work fine – if the flash is not where your camera is.
And the background is nice! But that is a mere accident: the flash is lighting up the white backdrop, too.
But what if we did not want this effect for the background? Say we want it to be back, or to be lit differently, or to have colour?
Well then is paramount to keep the face flash off the wall. And we do this by fitting a grid to the flash:
The grid restricts the area lit by the flash – basically it just lights a circle straight ahead. So now we get this:
So now we have a dark wall. That does not of course mean we need to keep it dark, but now where and how we light is is under our control. We could do these shots:
If we had not used a grid to keep the initial background dark, we could not have coloured it.
The D4 with the Nikon 24-70 performed very well, by the way!