- Step 1. Load a 35mm camera with ISO 400 film or set a digital SLR camera's ISO to 400. Mount the camera to a tripod. Attach the shutter release cable/cord to camera.
Step 2. Determine the hyperfocal distance or depth of field in order to figure out where to place the tripod-mounted camera in relation to the first item of evidence in the scene. The following information can be used as a quick reference:
Lens F = Stop (Aperture)
F22 = 12 feet min. — Tripod-mounted camera will be 12 feet from first item of evidence.
F16 = 17 feet min. — Tripod-mounted camera will be 17 feet from first item of evidence.
F11 = 24 feet min. — Tripod-mounted camera will be 24 feet from first item of evidence.
F8 = 34 feet min. — Tripod-mounted camera will be 34 feet from first item of evidence.
Everything from above distances to infinity will be in-focus when using the respective aperture F-stop settings of the lens set at a focal length of 50mm.
Step 3. Determine flash alley positions. The photographer needs to know the effective range of the flash unit. Each flash unit has a guide number for the film's ISO setting. For digital cameras, the selected ISO number will be used. The photographer will take the flash unit's guide number for the selected ISO and divide that number by the aperture (F-stop) selected on the range. For example, a Quantaray flash unit will have a guide number of 198 with ISO 400. Take 198 and divide it by 16, and it equals 12.37. We will round this number down to 12, indicating that the maximum effective range of this flash unit when using an ISO setting of 400 and an aperture setting of F16 is 12 feet. Flash positions will need to be spaced 8 to 10 feet apart to allow for flash overlap.
Photographers can then calculate the minimum number of flash positions needed for a particular scene. In the diagram on Page 53, the scene is 30 feet deep. The maximum effective range of the flash is 12 feet, thus there will need to be at least three flash positions at least 10 feet apart down each side of the scene. Spacing the flash units in this way allows for a 2-foot overlap of each unit's maximum effective range.
With the camera lens set on the 50mm focal length, the angle of view from the camera lens will be approximately 30 degrees from the lens to the left and right. The flash alley will be 90 degrees to the camera running parallel down each side of the crime scene. These positions will be to the right and left of the camera, running parallel to scene and the direction the camera is pointed. Each flash position will be an equal distance from the previous position. The total number of flash positions for the scene will be determined by the length and width of the scene and the mathematical formula previously explained.
Flash Position 1 will be within the camera's angle of view. This position should be about half-way between the right edge of the camera's angle of view just before the farthest item of evidence from the camera in the scene. The photographer must look through the camera's viewfinder to help the assistant determine the location. Once the spot for Flash Position 1 is determined, the assistant should place a marker on the ground for later reference.
Flash Position 2 also will be within the camera's angle of view, but closer to the right edge of the angle of view. Once the spot for the second flash position is determined, another marker should be placed on the ground for future reference. Flash Position 2 should be an equal distance between Flash Positions 1 and 3.
Flash Position 3 will be outside the camera's angle of view and an equal distance between the camera film/sensor plane and Flash Position 2. Once Flash Position 3 is determined, a marker should be placed on the ground for future reference.
Flash Positions 4, 5 and 6 will be parallel down the left side of the scene directly across from Flash Positions 1, 2 and 3.
Flash Positions 7 and 8 will be outside the angle of view and an equal distance between the camera and Flash Positions 3 and 6. These flash positions, as well as any additional flash positions, will help eliminate shadows and add supplemental lighting to the scene. Although Flash Positions 1, 2, 4 and 5 are within the camera's angle of view, the silhouette of the assistant triggering the flash will be cancelled by the subsequent flashes. For example, Flash Position 1 will be cancelled after the flash is fired from Flash Position 2, and Flash Position 2 will be cancelled once the flash is fired from Flash Position 3. The same applies with Flash Positions 4, 5 and 6.
- Step 4. The photographer should focus the lens on an item approximately one-third of the way into the crime scene. This will assure that all items of evidence and other items in the crime scene will be in focus. If there are no items of evidence in the area of focus, the photography assistant can stand in the area one-third of the way into the scene and the photographer can focus the lens on the assistant. If using an auto focus lens, the photographer will need to switch it to manual focus mode to accomplish this step.
- Step 5. The photographer must set the shutter on 35mm film cameras to the "B" setting on the shutter control knob. If using a digital SLR, the photographer sets the camera to manual mode and the shutter to its "Bulb" setting.
- Step 6. The photographer should hold a flat black card over the lens opening to block any ambient light present. Once the flat black card is covering the lens, the photographer will depress and lock the shutter release button on the remote shutter release cable/cord.
- Step 7. The assistant will move to Flash Position 1. With a charged flash, the assistant will hold the flash at waist-level with the flash aimed parallel to the ground, 30 degrees into the scene away from the camera. Once the flash is charged the assistant will announce "Ready."
- Step 8. Once the photographer hears the assistant's announcement, he lowers the flash black card from in front of the lens and announces "Flash." The assistant then manually triggers the flash. After the flash is observed, the photographer places the flat black card back over the lens. The assistant then turns to the right with his back toward the camera. Once the flash has re-charged, the assistant again announces "Ready," and the photographer lowers the card in front of the lens and announces "Flash." The assistant again manually triggers the flash. Once the flash is observed, the photographer puts the card back over the lens. The assistant then turns 30 degrees to the right, aims the flash 30 degrees away from the scene, and the "Ready," "Flash," cover sequence repeats. Steps 7 and 8 will then be repeated at Flash Position 2. At Flash Position 3 this sequence will only be performed with the flash triggered 30 degrees into the scene and 90 degrees from the camera. The entire Step 8 sequence will be repeated at Flash Positions 4, 5 and 6. At Flash Positions 7 and 8, the assistant will utilize the same sequence as in Flash Positions 3 and 6.
By approaching any crime scene photography task in a slow methodical manner, analyzing your available light, and selecting the proper equipment, any crime scene photographer or investigator will be able to identify and use the best flash photography methods available.