ABSTRACT
This chapter illustrates methods in which capturing more than one image of an impression (fingerprint, shoeprint) can provide greater opportunity for improving the clarity and strength of that image. In the realm of digital imaging, so much more is possible in terms of optimizing signal-to-noise ratio. Images can be combined or blended in several ways, including the four basic functions in arithmetic—addition, subtraction, multiplication, and division. Erasure subtraction is an option for impression evidence that is obstructed and unusable, beyond the reach of less invasive strategies. The subtracted image in grayscale reveals an increase in the strength of the image, but there is still obstruction from the background. The goal of any forensic photographer should be to ensure that every evidence capture is the clearest, sharpest, and most complete possible. The importance of aperture selection is perhaps less well understood than other exposure factors.
