MACRO PHOTOGRAPHY

Macro photography is close-up photography. The classical definition is 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 (for example), 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 is that lenses designed for macro are usually at their sharpest at macro focus distances and are not quite as sharp at other focus distances.

In recent years, the term macro has been used in marketing material to mean being able to focus on a subject close enough so that when a regular 6×4 inch (15×10 cm) print is made, the image is life-size or larger. With 35mm film this requires a magnification ratio of only approximately 1:4, which demands less of lens quality than 1:1. With digital cameras the actual image size is rarely stated, so that the magnification ratio is largely irrelevant; cameras instead advertise their closest focusing distance.

Macroscopy competes with the digital microscope where a small camera tube can be attached directly to a computer, usually via USB port. Macroscopy also competes with photomicroscopy, and it is much less expensive to achieve high quality images. However, high magnification images are more difficult using macroscopy.

The method is especially useful in forensic work, where small details at crime or accident scenes may often be significant. Trace evidence such as fingerprints and skid marks is especially important, and easily recorded using macroscopy. Fracture surfaces from broken products are very revealing using fractography, especially when photographed using glancing light to highlight surface details.