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In my last column, I talked about different flash systems. The purpose of the flash is to throw light on whatever it is you are photographing. Once light has bounced off a subject, it has to be channeled to the camera's sensor to capture the image. This is the job of the lens, to channel the light. The lens can do other things, too.
Let's start with a typical digital camera setup for dentistry. The standard type of lens is a macro lens, usually 100 mm in focal length. For purposes of this column, I will be discussing the Canon EF (electronic focus) 100 mm Macro USM (ultrasonic motor) lens. Depending on the brand of camera, your lens may be 105 mm, or something similar. Using the Canon 100 mm Macro lens as our base unit, we will compare other lenses to it. When a lens is referred to as a macro type, this means that the lens is designed to take closeup views of small objects such as flowers, insects, and teeth. For dentistry, the ability to focus closely on small objects is essential. The 100mm length allows us to be eight to 20 inches from a patient yet still take a closeup view, such as a single incisor. A macro lens can take a portrait image that looks just like any other lens was used. But, since the macro lens is designed to focus up close, you need...