I was doing a photo shoot a few days ago, where I was photographing a lemon suspended from a piece of thread. I wanted to make it look as if it was hovering in pitch darkness.
Upon seeing the results, someone asked me an interesting question: Isn’t it difficult to focus your camera in the dark? Well, no, because the photo was taken in the daytime, with my lights on. So, how come does it look like it was taken at night?
That, my friends, is the power of contrast in lighting. You have to remember that you don’t need a dark room in order to make a background completely dark – you just need to ensure that your foreground is significantly brighter than the ambient light. Here’s how and why…
It’s all about relative brightness
To take the lemon photograph, I used a pretty simple set-up: A couple of flashguns aimed at the lemon, from a very close distance. Because the flashes were so close to the subject (they are just out of frame, in fact), it adds a lot of light. If you’re curious why that is, check out the inverse-square law on Wikipedia.
The reason why the photo came out as it did, is because of the camera settings: The camera was set to ISO 100, with f/9.0 aperture and 1/200 second shutter time. If you can’t visualise what those settings would do in the circumstances described, I welcome you to try that right now. Don’t worry, we’ll wait. Set your camera to precisely those settings, and take a photo indoors, without using a flash.
If you can’t be bothered to do the experiment: Even in a relatively well-lit room, that will result in a very dark photo indeed.
So, as far as the camera is concerned, it is taking a horribly underexposed photo. Which is perfectly fine, because I want a dark background. It’s the foreground that is important, and that is where my flashes come in.
Let me get this straight, you’re taking photos that look like darkness in a well-lit room?
This portrait was also taken in a relatively well-lit room - but again, because of the high flash output and the fast shutter time (in this case, f/8.0 and 1/500 second at ISO 100), it looks like it's taken in pitch darkness. Groovy. Clicky for bigger.
Short answer: Yup.
Slightly longer answer: Yup. You can do this by settin your camera to manual, and use an exposure which results in a dark room (by choosing a fast shutter time). The next step is to use your flashes to light the subject.
Of course, this doesn’t work if the light from your flashguns spill onto the background (you’re trying to keep that as dark as possible, remember?) so it is a good idea to use a snoot or a honeycomb grid to ensure that the flash light isn’t accidentally re-lighting your background, because then you’re back to square one.
Can this be used for anything else?
Well of course. Always remember that it’s all about the contrast in lighting: If your flashes are more powerful than the light you are photographing in, then you can ‘darken the room’ with your camera settings, and use the flashes to light your scene.
Hell, if you’ve got enough flashes, you can turn even broad daylight into night. Don’t believe me? Check out this article on ganging flashes, and scroll down to “Turning Noon Into Night With High-Speed Sync”. Pretty impressive stuff, but there’s a pretty ridiculous amount of money in flash equipment being used right there.
You don’t have to go to those extremes, though – using flash outdoors on a shady day can give great effects, because when done well, your subjects look as if they are brighter than the surroundings. When done subtly, it can look bloody fantastic – your eyes are automatically and subconsciously drawn to the main subject – always a good sign in a photograph.