Macro photography

Macro photography, also called photomacrography or macrography, and sometimes macrophotography, is extreme close-up photography in which the subject is reproduced at greater than its actual size. Macro photographs usually feature very small subjects and living organisms like insects.

Definitions

The optical reproduction ratio is the subject size captured on the film frame compared to the actual subject size, and is a function of the lens design. The optical magnification is equivalent to optical reproduction ratio. For example, an optical reproduction ratio of 1:10 means the image is recorded at th of the actual subject size, and the equivalent optical magnification is ×, 0.10×, or 10%. In the strictest definition, a macro photograph is one in which the size of the image captured is life-size or larger compared to the original subject.
File:Minolta 100-300mm lens with ratios.jpg|thumb|right|Minolta Zoom-Rokkor 100–300mm lens with markings for reproduction ratio
Building on this, a macro lens is therefore a lens capable of optical reproduction ratios of 1:1 or greater. Rudolf Kingslake gives a broader definition of a macro lens as one "which is well corrected for use over a wide range of object distances."
Since the size of the image on the negative or image sensor rarely is the subject of discussion except in technical photography and film-based processes, the final image is a more relevant measure of displayed size. Define the final magnification as the image size on the final print divided by the original object size. This definition of final reproduction ratio compares the size of the finished image, as displayed, with the actual size of the subject. Because the displayed image usually is larger than the film frame or image sensor, the final reproduction ratio is the product of the optical reproduction ratio and the magnification in reproducing the recorded image from the sensor or film to the display.
This means the subject will more likely be displayed at greater than life-size, and so the final displayed image more commonly lends a photograph macro status. For example, when producing a print using an image captured on a 35 format film or sensor, the printing process results in an inherent 4:1 magnification in going from the sensor to the print, which means a life-size result is possible with a lens set at a 1:4 optical reproduction ratio.

Term	Typical mag.
Close-Up	0.1 – 0.5×
Extreme Close-Up	0.5 – 1.0×
Macro	1.0 – 35×

Using the more expansive definition provided by Kingslake and considering the final reproduction ratio, many photographic lenses designed and sold with "macro" focusing ranges actually fall into the "close-up" range of optical magnifications, with a maximum optical reproduction ratio between 1:2 and 1:1. However, even 1:2 is significantly larger than non-macro lenses, as those often are designed with a maximum reproduction ratio of approximately 1:10 for practical and optical considerations.
Reproduction ratios much greater than 10:1 are considered to be photomicrography, often achieved with optical microscopes.

History

The term photo-macrograph was proposed in 1899 by W. H. Walmsley for close-up images with less than 10 diameters magnification, to distinguish from true photo-micrographs.
Development of the photo-micrograph led to the evolution of macro photography.
One of the earliest pioneers of macro photography was Percy Smith, born in 1880. He was a British nature documentary filmmaker, and was known for his close-up photographs.

Equipment and techniques

Macro lenses

Lenses with a "macro" focusing feature are specifically designed for close-up work, with a longer barrel extension mechanism than conventional lenses and optics optimized for high reproduction ratios; these are the most common tools for macro photography. Most modern macro lenses focus continuously from an optical reproduction ratio of 1:1 or 1:2 to infinity and can provide excellent optical quality for normal photography, although these should technically be called "close-up" lenses instead.
When using these "macro" lenses at a reproduction ratio greater than 2:1, they should be reversed. Alternatively, a teleconverter may be used with a "macro" lens to achieve reproduction ratios of up to 6:1 with reasonable working distances. For classic "macro" lenses, the focal length is fixed and all of the optical elements move as a unit during focusing. The magnification can be computed from the extension distance and lens focal length :
More recent macro lens designs include "floating" elements, which decrease the amount of extension needed to achieve a 1:1 optical reproduction ratio and facilitate autofocus operation. The effective focal length for lenses with floating elements typically decreases at minimum focus, and the effective focal length can be determined by comparing the observed lens extension for a given magnification to those same values at a reference point:
True macro lenses offer a maximum optical reproduction ratio of 1:1 or greater, such as the Canon MP-E 65mm f/2.8 1-5x Macro, Laowa 25mm f/2.8 2.5-5X Ultra Macro, Yasuhara Nanoha 4–5X, or Minolta AF 3x-1x f/1.7-2.8 Macro; by achieving higher magnification than life size, photographs can be taken of the structure of small insect eyes, snowflakes, and other minuscule objects. However, these lenses generally lose the ability to focus to infinity and cannot be used for general purpose photography. Others, such as the Infinity Photo-Optical's TS-160 can achieve magnifications from 0-18× on sensor, focusing from infinity down to 18 mm from the object.
Macro lenses are sold with different focal lengths for specific uses:

Continuously-variable focal lengthsuitable for virtually all macro subjects
"Normal" 45–65 mmgeneral purposes: product photography, document reproduction, small objects that can be approached closely without causing undesirable influence, and scenes requiring natural background perspective
"Portrait" 90–105 mminsects, flowers, and small objects from a comfortable distance
"Telephoto" 150–200 mminsects and other small animals where additional working distance is required
Mechanical extension

Extending the distance between the lens and the film or sensor, by inserting either extension tubes or a continuously adjustable bellows, is another equipment option for macro photography. As the lens is extended further from the film or sensor, the closest focusing distance decreases, the magnification increases in direct proportion to the lens extension; recall that. In addition, the image exposure needs to be increased when focusing closer, whether by using a slower shutter speed or wider aperture.
For many "macro" lenses with a maximum optical reproduction ratio of 1:2, a specific accessory extension tube often is available with a fixed extension distance of ; with it mounted, the "macro" lens loses infinity focus but the focus range can be adjusted from 1:2 to 1:1.
Generally, extension tubes are rigid and provide a fixed increase in distance, and bellows are flexible, allowing a variable increase in distance. The extension range of bellows generally varies between, resulting in a range of potential magnifications between 1:1 and 4:1 using a 50 mm lens. Tubes of various lengths can be stacked, decreasing lens-to-subject distance and increasing magnification. Some tubes incorporate a focusing helicoid which provide a variable extension length, albeit more limited than the potential range of extension when using a bellows; the extension tube equipped with a helicoid generally offers more rigidity and durability than a bellows.
Bellows or tubes shorten the available maximum focus distance and generally make it impossible to focus to infinity. To maintain infinity focus, special short-mount lenses may be available for use with bellows; these specialized lenses usually have just an aperture control without a focusing helicoid, as focusing is handled by the bellows itself.

Auxiliary lenses

Placing an auxiliary close-up lens in front of the camera's lens is another option. These are generally inexpensive screw-in or slip-on attachments that will reduce the closest focusing distance. The possible quality is less than that of a dedicated macro lens or extension tubes; some two-element auxiliary lenses are very good while many inexpensive single element lenses exhibit chromatic aberration and reduced sharpness of the resulting image. This method works with cameras that have fixed lenses, and is commonly used with bridge cameras.
The optical power of these auxiliary close-up lenses are measured in the dimensionless value of diopters, where the diopter is equal to the reciprocal of the focal length of the auxiliary lens, in meters. In other words,

Diopter	= Working dist.	Mag.
+0.5		×
+0.7		×
+1.0		×
+1.5		×
+2.0		×
+3.0		×
+4.0		×
+5.0		×
+10.0		×

The working distance of the combination of the host lens and auxiliary lens is equal to the focal length of the auxiliary lens when the host lens is set to infinity. In other words, the working distance, defined as the distance from the lens to the subject, can be computed from the diopter as:
When a close-up lens is attached, the host lens loses the ability to focus to infinity, but the host lens may be focused closer to increase the reproduction ratio. However, it may be more convenient to simply shift the entire camera and lens towards or away from the subject to find the correct focus.
The approximate magnification of the combined host and auxiliary lenses is the ratio of the focal lengths, which can be rewritten in terms of diopters:
The effective combined focal length can be computed from the original focal length of the host lens and diopter:
For example, consider the combination of a close-up lens with a diopter of +1.5 and a 50 mm host lens. The focal length of the close-up lens by itself is m, or mm. When the host lens is set to infinity, the combined working distance is and the combined focal length is mm, giving a magnification of ×. Because the resulting combined focal length is not much different than that of the host lens, virtually no exposure compensation is required.
If the same +1.5 close-up lens is used with a 28 mm wide-angle or 105 mm telephoto lens, the combined working distance remains the same, but the combined focal length changes to mm with the 28 mm lens and mm with the 105 mm lens, and the resulting magnification is × and × for the 28 mm and 105 mm respectively, which is approximately half and double that magnification using the same auxiliary close-up lens with the 50 mm host lens.
If a +0.7 diopter auxiliary close-up lens is used with a 105 mm telephoto lens, the working distance is and the combined focal length is mm, giving a magnification of ×, which is almost the same magnification achieved using a +1.5 diopter with a 50 mm lens. This means that increasing the focal length of the host lens will result in a greater working distance while maintaining a given magnification by using a weaker close-up lens.
Auxiliary close-up lenses can be stacked to achieve the desired magnification. The higher-powered lens should be attached closer to the host lens. In general, when using close-up auxiliary lenses, magnification should be limited to a maximum of 1:2 and the host lens should be stopped down.