How to Take a Forced Perspective Photo
The process for taking a forced perspective picture varies depending on they type of forced perspective image you are creating. As such, I’ve broken down the instructions by type of image.
How to Take a Size Changing Forced Perspective Photo
Depth of field, distance, and line of sight are the three main ingredients in a size changing forced perspective photo. This is the same technique used in the movies for decades before computer graphics came along. Darby O’Gill and the Little People is a great example of a movie made using forced perspective.
When creating this type of photo, the subject you want to appear smaller should be further from the camera than the subject you want to appear larger. Distance depends on the amount of size difference you want to achieve. To shrink a pet you might only need 6 or 8 feet. To shrink a mountain you might need a mile or more. Also, the larger the size difference between the actual size and desired appearance, the more space needed as well.
Most of these photos will be made with a wide angle lens (35mm or less) and a large F-Stop setting. The exact F-Stop required will depend on the distance between the two subjects. Use whatever setting is needed to put both subjects in focus. If you do not have manual focus control on your camera you can set the autofocus 1/3 behind your closest subject because DOF falls 1/3 in front of the focal point and 2/3 behind the focal point.
Once you have determined the focus for your photo, you’ll need to set up the alignment. If the subjects are not touching in the photo the alignment of the shot is not as critical as it is when the subjects appear to touch. If you are setting up a photo where the subjects appear to touch, such as one person appearing to stand in another person’s hand, you may need a tripod to get the stability you need for fine adjustment to the line of sight so that you don’t have gaps and overlaps of subjects in the wrong spots.
How to Take a Merged Subject Forced Perspective Photo
To merge subjects, such as the current trend of old photographs held in front of current versions of the same scene, you’ll follow the same process as the size change forced perspective photos only instead of emphasizing size differences you’ll make the old photo/sketch match the size of the current scene. Because you’ll be holding the old photo/sketch (relatively close to the camera), the large F-Stop (small aperture) and wide angle lens will be especially important to get both items in focus.