Forensic Dentistry, Second Edition

216 Forensic dentistry

11.8 Digital Photography

The modern era of photography is being redefined as the digital era. While
film-based cameras are still around, most forensic photography is done with
digital cameras. Manufacturers have created a wide range of digital cameras
that vary in both capabilities and cost. The new generation of digital cameras
has everything from the simplest point-and-shoot consumer camera to the
most complex professional camera, and a combination of several “pro-sumer”
cameras in between.
Digital image capture is unlike film in that a specialized computer chip
in the camera reads the light coming through the lens and electronically saves
the image on magnetic media, eliminating the need for film. Typical image
capture devices used today include the charge coupled device (CCD) and com-
plementary metal-oxide semiconductor (CMOS). CCD sensors are arranged
with geometric green, red, and blue areas known as pixels that are sensitive
to their corresponding colors of light. Typically there are two green pixels for
every red or blue pixel in an arrangement known as the Bayer pattern image
(Figure 11.14). Other manufacturers have developed other image capture
technologies, including the Foveon layered model and the six-sided pixel
technology from Fuji (Figures 11.15 and 11.16). The density of the pixels on
the sensor and the firmware driving the electronics in the camera determine
the quality of the image. Generally speaking, the more pixels there are, the
sharper the image. For bitemark photography, the larger the image file size,
the less pixilation (blurring) when enlarging to life-size proportions.

G B

RG

Figure 11.14 Bayer model. (source: http://www.photo.net/learn/raw)) rGB = red, blue,
green. each pixel in the sensor responds to either red, green, or blue light. there
are two green sensitive pixels for each red and blue pixel because the human eye
is more sensitive to green. (see color insert following page 304.)