Darkness descends upon the earth. A cold, lifeless body lies on the ground amidst a field of evidence beckoning to give up the secrets of what had occurred only several hours ago. A knight dressed in blue stands at the edge of the abyss, as a cool breeze blows in the nighttime air. A chill runs down his spine as he contemplates what he is about to undertake …
Could this be an excerpt from a best-selling suspense novel? More likely this describes the feeling many novice, and even veteran, crime scene photographers experience when faced with the prospect of shooting a crime scene in total darkness or very low-light situations. Although low-light and nighttime crime scenes can be challenging to even the most seasoned crime scene photographer, with the proper equipment, a little training and a good dose of practice, documenting night scenes can become almost as routine as capturing scenes with ample lighting.Essential equipment
With the proper equipment, any crime scene photographer can take nighttime photos that look as if they were shot during the day, and remove pesky shadows to make even the darkest items appear as though they were photographed in a studio.
The following is a list of essential equipment for low-light and nighttime photography:
- 35mm or digital SLR camera with a hot shoe
- Flash unit with fresh and spare batteries or rechargeable battery pack
- Off-camera flash cable
- Remote shutter release cord
- Fill flash
Many times items of evidence are found under a car, tree or other obstruction that casts shadows over the evidence and causes the photo to appear underexposed. The fill-flash technique helps photograph items obscured by shadows. When using this method, the flash mounts to the camera via the off-camera cord. This allows the photographer to aim the flash in the direction of the evidence. When the flash fires, the light it produces removes the shadow and illuminates the item.
When using this technique for items under a car, the photographer will take a midrange photo from a natural perspective using a 50mm lens focal length. A flashlight can be used to illuminate the evidence for lens focusing purposes. After focusing the lens, the photographer should aim the flash in the direction of the item being photographed. If the item being photographed lies in the shadow of a tree or other obstruction, and the photographer cannot position himself with the sun to his front, a fill flash technique can be used to remove the shadow cast by his body or the obstruction. The photographer simply focuses the lens and holds the flash above him or level with the camera aiming at the item. Any shadows will be eliminated when the flash fires.Oblique lighting
Oblique lighting, sometimes referred to as cross lighting, is another useful tool. Prior to entering a crime scene or area where evidence is located, the crime scene photographer should get on his hands and knees and shine a flashlight perpendicular to the floor. Using this technique, oblique lighting may yield trace evidence that may not be seen from a standing position.
This same technique is also useful in crime scene photography, particularly regarding written documents in suicide cases, prescription fraud, forgery and check fraud cases. When a person writes on the top page of a tablet of paper, the writing indents on subsequent pages of the notepad. In suicide cases where a victim is found in a location with a single-page note nearby, questions may arise as to who wrote the note or where the note was written. If the notepad can be located, investigators can check for indented writing on the remaining pages to determine where the note was written and possibly, through handwriting analysis, if the victim wrote the note. Photographers can use oblique lighting to help document this impression evidence as well as tire and shoe impressions and patent (plastic) fingerprints.
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.
- 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.