So you are outside and want to darken the background for a mixed light picture. You’ve heard me talk about this repeatedly.

What can you do? Yes, the triangle, of course. Aperture smaller, shutter faster, ISO lower. But which do I prefer?

Outside in bright conditions your flash is competing with the sun. So you do not want to reduce effective flash power. Yet both aperture and ISO do not just reduce the background: they also affect the effective flash power.

So in those conditions:

1. You start with the shutter, always. As fast as you can, which is the shutter sync speed: 1/200th sec on cheaper cameras, 1/250th on most, and 1/300th on some (like my 1D  Mk IV). Go to that speed.
2. Then, and only then, if you still need to darken more, start messing with higher “f-numbers ” or lower ISOs.
3. If you now end up with insufficient flash power? Add flashes. Bring the flash closer. Use more powerful flashes. Zoom in with your flash heads. Or as a last resort, wait until the light is less intense.

Simple rules make the technical aspects of photography simple and that is what we want.

After the click, an image taken thus at 100 ISO at 1/300th at f/6.3. (It’s a slightly NSFW image so it is after the click. For those of you uncomfortable with the unclothed human body, like those of you in Anglo-Saxon or Muslim countries, or who buy at large photo retailers in Ontario: you may not want to click. Everyone else: click away, it’s entirely harmless!):

So the 1/300th was needed to get a nice darker (i.e. saturated!) background, rocks, and unlit-side-of-model. The (off-camera, on our right) flash lit up the subject (using an umbrella). I had to go to f/6.3. If I had had to go to f/8, say, the small flash (a 430EX) would have had insufficient power.

I lost my second 580EX the other day-  if anyone found it let me know. I have/had two 580EXs and four 430EXs. Darn!