What does the focal length of the lens mean?
The focal length is the distance from the center of the lens to the focal point – the point where the rays of light converge and are in focus. It is important to know the focal length of the lens when selecting lenses for specific tasks. For example, the focal length decreases as power increases, so it requires great care to work close-up using a high-powered lens. • What is depth of field? Depth of field is the portion of the magnified area that is in focus. As power increases, the depth of field decreases. Under some conditions you must choose between the depth of field and the amount of magnification you require. • How important is light to magnification? Both light and magnification are important for best viewing results. With proper lighting, less power is needed in magnification, which allows a larger field of view and a better working distance under the lens. Choose carefully when selecting an illuminated magnifying lamp. • What kind of diopter/power relationships am I likely to
