6.6: EXTREME CLOSE-UP OR MACRO-PHOTOGRAPHY

As previously mentioned, close-up or evidentiary photography is important to capture images of individual items of evidence. These images can either be evidentiary photographs, where a sharp image of the item of evidence is required for identification or demonstration purposes during court proceedings, or comparison quality photographs needed by an analyst to compare the item of evidence with a known exemplar, such as fingerprint or other impression evidence. In this second category of close-up photographs is the macro-photograph, which is a highly detailed image that creates an image of a very small object that appears to be larger in comparison to the original object. Macro-photographs allow the analyst to detect and demonstrate minute striations, indentations, or defects that are individual to the item of evidence. These photographs require a camera with high resolution and a stable shooting platform, like a copy stand. A good tripod can be used to support the camera in the field, but that tripod must have a center post that can be reversed so that the camera can be mounted in a manner to allow it to photograph between the legs of tripod, or one that has an extendable boom arm.

Figure \(\PageIndex{1}\): Your author's macro-photography camera in his laboratory. Note the three-bubble level on the hot-shoe. - Author's collection

Distortions

Distortions occur in macro-photography when the resulting image has lines that appear curved or bulging, or one side of the image appears slightly larger than the other side of the image. Distortion are either caused by the lens of the camera or the camera being askew to the item being photographed. Either way, the resulting image will not be an accurate representation of the image and can cause errors in analysis. Therefore, it is important to use a good, dedicated macro-lens that minimizes barrel distortion, where the image bulges out in the center of the frame, and the camera is positioned parallel to the item. This can be accomplished using a three-bubble level that matches the camera’s film or sensor plane with the item being photographed.

Same Plane Photography

As previously mentioned, it is imperative in macro-photography that the image must include a scale, and the scale must be on the same plane as the part of the object desired to be photographed. If the scale is slightly lower or higher than the object, the auto-focus feature of the camera may attempt to focus on both the object and the scale, resulting in both the scale and the object being slightly out of focus. If the photographer turns off the auto-focus feature and focuses the lens manually, either the scale or the object may be slightly out of focus. Carefully positioning the scale at the exact same height as the evidence item will correct this form of distortion. Furthermore, when photographing impressed footwear or tire tread, it is important to place the scale at the same level as the impression. Failing to do this will cause image distortion that will adversely affect comparison efforts.

Figure \(\PageIndex{2}\): Same plane photograph with the scale even with the fired cartridge casing. Note the casing is curved and therefore the aperture was set at f22 for better depth of field. - Author's collection

Figure 6.6.4: Footwear impression. Note the scale has been placed in a trench at the same level as the impression. Author's collection

Fill the Frame

The attention of the viewer should be on the subject of the photograph and not the background or unrelated objects in the frame. Even when photographing an object that requires a ruler or scale, it is best to take one photograph with enough of the scale for the analyst to know if the object was measured in inches or feet, or millimeters or centimeters. However, the next photograph should have the object in the center and filling the frame, and only the divisions of the scale are needed for scaling purposes.

Figure 6.6.5:

The object is centered and filling the frame, and only the divisions of the scale are in the frame. Author's collection

The Macro Lens

The macro lens allows the photographer to capture highly detailed and sharp images that appear much larger than the original object being photographed. These lenses have shorter minimum focus distances than normal lenses. “True” macro lenses offer magnification of 1:1 ratio. This means that the subject appears on the camera’s sensor the same size as in real life. Some macro lenses offer magnification ratios of 2:1, or even 5:1. The drawback of the macro lenses are that they are very expensive and have an application that is limited in forensic photography mostly to laboratory use where the stability of the camera, the adjustment of light sources, and the necessary equipment and conditions exist to safely photograph the item with limited contamination or destruction to the item of evidence being photographed.

ISO Film Speed

The last topic to mention in close-up or macro photography is the ISO film speed. ISO film speed was originally the International Organization for Standardization rules representing the sensitivity of photographic film as designated by a numerical value. In the digital era, ISO represents the standards of the sensitivity to light of the camera’s sensor. ISO settings on most digital cameras vary between ISO 25 to ISO 6,400, or even higher. A high ISO film speed setting allows images to be captured in darker lighting conditions. A lower ISO film speed setting allows images to be captured in conditions with more available lighting. The drawback is that higher ISO settings tend to be grainy, especially when the image is enlarged. Lower ISO settings capture images that are sharper. Comparison quality photographs must always be captured using an ISO setting of 100 or less. In comparison quality or macro photography, the camera should be set at ISO 100 (or less), with an aperture of F18 to F22, and a shutter speed of 1/60th of a second; therefore, there are few people who can hand-hold a camera steady at those settings, and that is the reason a copy stand or good camera tripod are required for this type of photography.