Macro describes photography of very small subjects at close range, so they appear large in the picture. It also describes the equipment used for it, such as macro lenses and extension tubes.
In the strict sense, a macro photograph shows the subject at life size or larger on the sensor or film. This is a magnification ratio of 1:1 or greater. A true macro lens can reach at least 1:1. Many lenses labeled "macro" only reach 1:2 or 1:4, so they are better described as close-up lenses.
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