A macro lens is used for Macro photography and it refers to close-up photography; the classical definition using a macro lens is that the image projected on the "film plane" is close to the same size as the subject. On 35 mm film , the lens is typically optimized to focus sharply on a small area approaching the size of the film frame. Most 35mm format. A macro lens achieves at least 1:2, that is to say, the image on the film is 1/2 the size of the object being photographed. Many 35mm macro lens have 1:1, meaning the image on the film is the same size as the object being photographed. Another important distinction is that a macro lens is designed for macro are usually at their sharpest at macro focus distances and are not quite as sharp at other focus distances.