A specialist lens designed for the purpose of carrying out macro photography.
Macro lenses achieve a life size representation (on the sensor plane) of small objects by allowing very close focusing of the lens. Typically, the macro lens has a long barrel but a close focus range (usually less than half a metre).
The macro lens’ ability to focus at close range creates a very shallow Depth of field when focusing on close objects. A small aperture (high f-number) is required to enable an acceptable sharpness for small 3D objects.
The photographic subject-size on the digital sensor (or Definition: Sensor plane) compared to the actual subject size is known as the reproduction ratio. Images taken on a macro lens are typically 1:1 on the sensor plane. However, the print of a photograph taken with a macro lens will typically be larger than 1:1 in actual size.
Macro lenses normally have the ability to focus at infinity as well as in close to the lens. Focusing at infinity means that macro lenses can take ordinary photographs – ones that are not considered close ups. Some macro lenses which are in the range of 60mm to 100mm are often considered fine portrait lenses.
Lenses that have a reproduction ratio greater than 1:1 are normally referred to as photomicrographic lenses. These have the properties of a microscope (create a magnified image) and in the past have not been considered macro lenses. However, with the improvements in lens technologies in recent years some manufacturers have achieved higher than 1:1 reproduction ratios and the lenses have still been called macro lenses even though there is a true magnification of the subject.
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