Ever wanted to be haunted? Ok I don't believe in that kind of stuff but the ability to place a shadow that is interacting with the background opens the door for a lot of artsy concepts.
Step 1: Supplies
For this technique you will need
a camera with long exposure settings
a flash unit with a test fire button.
The flash unit is key because it allows you the sharp edges or a normal exposure time. The unit does not need to be compatible with the camera or even designed to work with digital. For this guide I used a Sunpak 221d which goes for about 20 dollars. Foreseeability you could use alternate light sources and that will be discussed towards the end of this guide.
Step 2: Setup
Set up your frame however you like but the area needs to be fairly dark. because of how the camera sensor works moving around in the dark wont show up after the flash fires and illuminates the whole scene with stronger light then what ever exist in the dark. The set up photos were taken during the day for clarity. Once your camera is on the tripod and and the scene is staged set your cameras exposure to 30 seconds or longer. The aperture will vary depending on the light source and your desired to final image appearance. For most experimenting is the best way to figure correct exposure settings out.
Step 3: Execution
Press the button to start the exposure button and position your self in the image. If you have models even better. Place the flash unit on the opposite side of your body from the camera and test fire. If you want a second "ghost" in your image reposition so that the flash is aimed at a different surface from the first "ghost". Step back behind the camera and fire the flash unit one last time to light up the entire scene. 3 flashes from the flash unit was the most I could get due to the recharge time limitations but flash unit technology has changed a bit in the past few decades.
Step 4: Results
The site of the flashes for the ghost is going to be more light up. This could be addressed by breaking the whole scene exposure into a separate image and com positing the lighting for the rest of the scene with Photoshop and masks.
Things to watch out for include washing out once ghost with the flash from another as you can see on the knee of the ghost on the right. Also catching parts of the ghost in the flash that brings the color of their cloths into the final exposure instead of a rich sharp shadow.
Alternative light sources can be used but the light source needs to be fast to avoid the blurd edges. In the secound photo an astronomy laser was used. Although the legs are resonably sharp for a moving light source the movement of the head is quite visable in who blurry it's edges are. Moving the light quickly on the wall so it only contacts an edge of the body momentarily will create sharper edged.