What is a “Macro” Lens?
A “Macro” lens is specifically designed for close-up work. However, most modern macro lenses can also focus continuously to infinity, providing excellent optical quality. Technically to be considered a macro lens, it must be capable of render an image larger than life, in other words the resulting image is larger than the subject. But with the development of small image sensors for digital and video cameras, that definition becomes a bit obscured since a larger than life image can be created on a sensor array without producing it optically.
For practical purposes, a macro lens is sought out to focus on subject materials that are less than a few hundred millimeters from the lens, which is the working distance limit of most standard lenses.