Image Capture FIGUre 2.14 The difference between a full-frame (24 × 36 mm) sensor and an APS-sized sensor (23.6 × 15.8 mm). This gives a magnification, or "crop," factor of approximately 1.5×. Scanners as Close-Up and Macro Cameras Flatbed scanners are designed primarily for digitizing flat artwork or photographs, but can also be used to produce extremely high-quality close- up and macro images of three-dimensional objects, albeit with rather flat, noncontrollable lighting. While most scanners reflect light from the surface of solid objects, some have a "transparency hood" with a light source in the lid, which will pass through translucent objects. For close-up and macro work, choose a standalone scanner with a lift-up lid rather than a multifunction device, and one with a transparency hood area as large as possible. You will need a higher resolution of up to 10,000 dpi or more if you are going to scan very small objects. (Despite using a CCD containing pixels, scan resolution is usually quoted in dots per inch, which is easily confused with printer resolution also being quoted in dots per inch.) The ability of a scanner to record the highest level of shadow detail and midrange gray values is its optical density. Choose one with as large a figure as possible. 29