A medical camera refers to close-up photography with a medical distinction; the classical definition for a medical camera for macro photography that the image projected on the "film plane" (i.e film or a digital sensor) 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 macro lenses achieve 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 lenses are 1:1, meaning the image on the film is the same size as the object being photographed. Another important distinction for a medical camera for macro photography is that lenses designed for macro are usually at their sharpest at macro focus distances and are not quite as sharp at other focal distances.