How to Take Double Exposures Using Your Digital SLR
If you ever want to be beside yourself, you can use your digital SLR to take a double-exposure. A traditional double exposure is two images on one frame of film; because you’re working digitally — no film involved — you have to fake it.
A double-exposure requires a couple accessories and works better at night or in a dimly lit area because the shutter needs to be open for a long time.
Choosing camera settings for a double exposure with a digital SLR
To fake a double exposure with a digital SLR, your shutter needs to be open for 20 seconds or longer, so use the lowest ISO setting — 100 if you have it — and a small aperture of f/22. The small aperture gives you a tremendous depth of field, which enables you to move about freely in the frame without the worry of being out of focus. A focal length of 28mm to 50mm also gives you a large depth of field. Choose Aperture Priority mode and Single Shot focus with a single auto-focus point.
You need to mount the camera on a tripod or solid surface to stabilize it during the long exposure, which means you don’t need image stabilization.
Taking a double exposure
Creating multiple iterations of you or a friend in a single image requires a bit of planning. You have to compose the picture beforehand and know exactly where you want the subject to be when the shutter closes.
This technique creates a somewhat ghostly image. But if it’s too hard to see the person, switch to an area that has a darker background. Also, make sure the person in the picture wears clothing that contrasts with the background.
Mount the camera on a tripod or set it on a flat surface and make sure it’s level.
Enable the camera self-timer.
Most cameras have a ten-second self-timer, which gives you time to walk into the frame.
Compose the picture, and then press the shutter button halfway to achieve focus.
Focus on something in the middle of the scene. The small aperture gives you a huge depth of field, so you appear in focus anywhere in the frame.
Press the shutter button fully.
The self-timer starts counting down. On most cameras, a flashing red light starts blinking on the front of the camera. It starts flashing faster when the camera is about to open the shutter.
Have the subject — you or a friend — walk into the frame.
When the light stops flashing and the shutter opens, count slowly to ten while holding perfectly still.
At the count of 11, walk to another area in the frame and hold position until the shutter closes.
With a small aperture of f/22, the lens stays open for about 30 seconds.
If the shutter doesn’t stay open long enough, it’s not dark enough for a long exposure. You can move to a darker area, wait until it gets darker where you are, or use a neutral density filter to decrease the amount of light reaching the sensor, thereby increasing the duration of the exposure.