Metric Master Lens Converter

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Metric Master Lens

Diopters (D):

Focal Length (mm):

Magnification (X):

FAQ

Diopters (D) are a unit of measurement of the optical power of a lens or curved mirror. It is equal to the reciprocal of the focal length in meters (1/meter). A higher diopter value indicates a stronger lens, which will have a shorter focal length.

Focal length (f) is the distance from the optical center of a lens to the point where parallel rays of light converge (for a convex lens) or appear to diverge from (for a concave lens). The relationship is D = 1000 / f (where f is in millimeters), or D = 1 / f (where f is in meters). A shorter focal length corresponds to a stronger lens and higher diopter value.

In the context of a simple magnifying glass, magnification describes how much larger an object appears through the lens compared to viewing it with the naked eye at a standard reading distance. The formula used in this tool is a common approximation: M = (Diopters / 4) + 1. This assumes a standard reference distance of 250mm (10 inches) for comfortable viewing.