What Flash Diffusers Do
Cameras need light to create images, and when ambient light is low, an on-camera or external flash comes in very handy. As in so many things in life, though, sometimes the solution–in this case, the flash–creates a new set of problems.
Light from a flash can be harsh and overpowering and unnatural, adding hard shadows to subjects that don’t need them. In the case of portraits, flash often blows out some details, reveals unpleasant minutia, and as we already mentioned, forces ugly shadows into some images.
To avoid these kinds of problems, you need more diffused light, like the kind you see outside on a cloudy day. But how do you soften light from a flash? Well, you can buy a pricey diffuser, or you can simply make your own.
For more on flash diffusers, please read Flash Diffusers 101.
Pop-Up Flash Diffuser
Many digital cameras have pop-up flashes that are handy for snapshots. But these flashes are difficult to control in terms of direction and intensity, and they provide anything but diffused light.
Try to soften the light using a 3.5 x 5-inch notecard. Open your camera’s flash and wiggle the notecard gently into the seam between the camera and the flash. If this crease is too tight, don’t force the card into place; you may need to use a bit of tape to secure the card. Angle the card so that light bounces upwards.
Now experiment indoors and outdoors to see the results. In a room with a low, light-colored ceiling, you’ll see that light bounces off the card, up to the ceiling and back down towards your subject. You may need to manually increase your flash brightness using your camera menu to get the best images.
External Flash Diffuser
External flashes are great because they are more powerful and adaptable than pop-up flashes. Many also include built-in diffusers that slide out of the flash body and over the bulb.
However, a homemade diffuser may still be useful. Enter the always useful empty plastic milk jug.
More specifically, the 1/2-gallon plastic jug. These translucent jugs let a lot of light pass through but they also do a good job of scattering light in a pleasing way. Better yet, the plastic is extremely flexible, letting you cut and twist the plastic to fit your flash.
You don’t need a perfectly fitting piece of plastic. Try one six-inch strip from your 1/2-gallon jug. Place the center of the strip directly over your flash, bend the flaps down either side, and use a rubber band to secure it. Now shoot. The results will be immediately apparent.
You can add another layer to your diffuser to further soften the light, or you can reduce or increase the flash’s power for different effects.