Macro Lens
A lens corrected for close focusing that reproduces a subject at life size or larger on the sensor.
Formula / rule
m = image size / subject size
Measured in
magnification ratio
In depth
True macro means 1:1 magnification, where a ten-millimetre insect projects a ten-millimetre image. Macro designs correct for flat-field performance and low distortion at close range, which also makes them superb for copy work and product photography. Depth of field at these magnifications is measured in millimetres regardless of aperture.
Examples in practice
A 100 mm macro at 1:1 renders a housefly's compound eye across a third of the frame.