Oblique lighting is a process where the flash provides perpendicular lighting to the surface being photographed. The flash unit is connected to the off-camera flash cord, and the cord is connected to the camera's hot shoe. This technique can be done by one person, but is easier when completed with an assistant. The photographer controls the camera focusing and shutter release, and the assistant controls the flashlight and flash unit. The assistant holds the flashlight, which is turned on next to the flash unit head and pointed in the same direction. In the case of the notepad, the flashlight is used to illuminate the pad across its surface. The photographer then focuses the camera on the notepad directly above the notepad's top sheet. The assistant then slightly moves the flashlight's angle up and down, while the photographer peers through the viewfinder, until the optimum contrast is achieved. Once the photographer has determined the angle for optimum contrast, the assistant turns off the flashlight. At this point the flash unit should be at the same distance and angle as the flashlight. The photographer then presses the shutter release to take the photo.Bounce flash
When taking close-up photos, the flash unit itself may be too intense and cause unwanted reflections off items being photographed. Using a flash diffuser or technique called "bounce flash" helps eliminate unwanted reflections. Bounce flash also may be used to introduce controlled shadowing to highlight engravings and serial numbers.
Bounce flash is a flash photography technique where the photographer utilizes a reflective or flat white surface to bounce the light from the flash off in order to illuminate an item during mid-range or close-up photography. An assistant is needed to use this technique. First the photographer must attach the flash to the camera using the off-camera cord. Once the lens focal length and aperture are set, the photographer focuses the lens. The assistant aims the flash at the reflective surface, which is angled toward the evidence.Painting with light
Just as an artist uses paint and brushes to make a painting come to life, a crime scene photographer can use a flash unit to make nighttime crime scenes appear as though they shot during the day. Painting with light is the use of one or multiple flash units to introduce light in an otherwise dark unlit scene.
Depending on the amount of ambient light in the scene, painting with light can be accomplished by the photographer without assistance, but to obtain the best results a minimum of two people should be used. The following steps should be followed when painting with light.
- Identify scene type and any ambient light available. Is the evidence in the scene in an open field, a segment of roadway, located in a yard, the interior of a residence following a fire? Are there reflective surfaces that can be used to bounce the flash? Photographers should try to position their equipment to maximize any ambient light in the area. However, if the scene encompasses a roadway, officials will need to either stop traffic during the shoot or live with the fact that there will be streaks of light from passing cars in the photos. If the object being photographed is a fixed item, such as a house or car, the flash may reflect off windows, requiring the photographer to adjust his equipment and shoot the scene from an angle that minimizes reflective light. Shooting a scene photo of the front of a house, discharging the flash two times, one with the flash aimed at the front right corner and the other with the flash aimed at the front left corner allows the photographer to incorporate everything in the photo while eliminating the possibility of flash reflection in windows. The same applies when photographing automobiles. When shooting indoors where no electricity is available for lights, such as the inside of an arson scene, care must be taken to prevent the flash from reflecting off pictures, mirrors and windows.
- Equipment set up. Since this technique requires locking open the camera's shutter, a tripod and remote shutter release cable/cord are required.