TABLE OF CONTENTS There are several ways to combine images for different purposes. In Chapter 12 we looked at methods for combining multiple images into a court chart, and in Chapter 13 we looked at combining a sequence of images to create a single, high-resolution image. Chapter 23 includes a section on combining images to reduce image noise. In this chapter, we will look at how we can combine multiple photographs of the same image to show differences in lighting in the images.
The primary application for this technique is to show a well-lit scene or object with a laser bullet trajectory or to show a piece of evidence with a fluorescing stain.
Typically, photographs of fluorescing stains or laser trajectories have very dark backgrounds because of the need to show the laser or fluorescence. To show the scene or object under "normal" lighting requires a second photograph.
By combining the images, you can see the overall scene or object and the fluorescence or laser in the same image. With film, this could be done in the darkroom, by exposing a sheet of photographic paper with two negatives one of the overall object or scene and one of the fluorescence or laser. However, this can be difficult because the two images must be exactly aligned and the two print exposures must be made by trial and error.
Information from multiple images can become important in a case when you need to show the exact position or size of a fluorescing...
