Macrophotography
Macrophotography is close-up photography, usually of very small subjects. Classically a macrophotograph is one in which the size of the subject on the negative is greater than life size. However in modern use it refers to a finished photograph of a subject at greater than life size.[1] The ratio of the subject size on the film plane (or image sensor plane) to the actual subject size is known as the reproduction ratio. Likewise, a macro lens is classically one lens capable of reproduction ratios greater than 1:1, although it now refers to any lens with a large reproduction ratio, despite rarely exceeding 1:1.
Outside of technical photography and film-based processes, where the size of the image on the negative or image sensor is the subject of discussion, the finished print or on-screen image more commonly lends a photograph its macro status. For example, when producing a 6×4 inch (15×10 cm) print using 135 format film or sensor, a life-size result is possible with a lens having only a 1:4 reproduction ratio.
Reproduction ratios much greater than 1:1 are considered to be the realm of photomicroscopy, often achieved with digital microscope.
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[edit] Equipment and techniques
"Macro" lenses specifically designed for close-up work, with a long barrel for close focusing, are one of the most common tools for macrophotography. (Nikon designates such lenses as "Micro" because of their original use in making microforms, but most lens makers use the term "Macro" or "Makro.") These lenses are optimized for high reproduction ratios. Most modern macro lenses can focus continuously to infinity as well, using complex focusing mechanisms that alter the optical formula. In most cases these lenses provide excellent optical quality when used for normal photography, although a macro lens may be optimized to provide its best performance at its highest magnification. True macro lenses, such as the Canon MP-E 65 mm f/2.8 or Minolta AF 3x-1x 1.7-2.8 Macro, can achieve higher magnification than life size, enabling photography of the structure of small insect eyes, snowflakes, and other minuscule objects. Others, such as the Infinity Photo-Optical's TS-160 can achieve magnifications from 0-18x on sensor, focusing from infinity down to 18mm from the object. However, macro lenses with 1:1 or 1:2 ratios are more common, and many of these find frequent use for general photography because of their excellent optics.
Macro lenses of different focal lengths find different uses:
- Continuously Variable Focal Length — suitable for virtually all macro subjects
- 45–65 mm — product photography, small objects that can be approached closely without causing undesirable influence, and scenes requiring natural background perspective
- 90–105 mm — insects, flowers, and small objects from a comfortable distance
- 150–200 mm — insects and other small animals where additional working distance is required
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 macrophotography. The further the lens is from the film or sensor, the closer the focusing distance, the greater the magnification, and the darker the image given the same aperture. Tubes of various lengths can be stacked, decreasing lens-to-subject distance and increasing magnification. Bellows or tubes eliminate infinity focus. They can be used in conjunction with some other techniques (e.g., reversing the lens).
Placing an auxiliary close-up lens (or close-up "filter") in front of the camera's taking lens is another option. Inexpensive screw-in or slip-on attachments provide close focusing at very low cost. The possible quality is less than that of a dedicated macro lens or extension tubes, with some two-element versions being 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. These lenses add diopters to the optical power of the lens, decreasing the minimum focusing distance, and allowing the camera to get closer to the subject. They are typically designated by their diopter, and can be stacked (with an additional loss of quality) to achieve the desired magnification.
Photographers may employ view camera movements and the Scheimpflug principle to place an object close to the lens in focus, while maintaining selective background focus. This technique requires the use of a view camera or perspective control lens with the ability to tilt the lens with respect to the film or sensor plane. Lenses such as the Nikon PC-E and Canon TS-E series, the Hartblei Super-Rotator, the Schneider Super Angulon, several Lensbaby models, the Zoerk Multi Focus System, and various tilt-shift adapters for medium format, allow the use of tilt in cameras with fixed lens mounts. Traditional view cameras permit such adjustment as part of their design.
Ordinary lenses can be used for macrophotography by using a "reversing ring." This ring attaches to the filter thread on the front of a lens and makes it possible to attach the lens in reverse. Excellent quality results up to 4x life-size magnification are possible. For cameras with all-electronic communications between the lens and the camera body, such as Canon EOS, specialty reversing rings are available which preserve these communications. When used with extension tubes or bellows, a highly versatile, true macro (greater than life size) system can be assembled. Since non-macro lenses are optimized to for small reproduction ratios, reversing the lens allows it to be used for reciprocally high ratios.
Macrophotography may also be accomplished by mounting a lens in reverse, in front of a normally mounted lens of greater focal length, using a macro coupler which screws into the front filter threads of both lenses. This method allows most cameras to maintain the full function of electronic and mechanical communication with the normally mounted lens, for features such as open-aperture metering. The magnification ratio is calculated by dividing the focal length of the normally mounted lens by the focal length of the reversed lens (e.g., when an 18 mm lens is reverse mounted on a 300 mm lens the reproduction ratio is 16:1). The use of automatic focus is not advisable if the first lens is not of the internal-focusing type, as the extra weight of the reverse-mounted lens could damage the autofocus mechanism. Working distance is significantly less than the first lens.
Depth of field is extremely small when focusing on close objects. A small aperture (high f-number) is often required to produce acceptable sharpness across a three-dimensional subject. This requires either a slow shutter speed, brilliant lighting, or a high ISO. Auxiliary lighting (such as from a flash unit) is sometimes used. Uniform lighting can be difficult with subjects very close to the lens, so a ring flash is often used, especially when working distance is small. Good results can also be obtained by using a flash diffuser.
[edit] Technical considerations
[edit] Depth of field
Limited depth of field is an important consideration in macro photography. This makes it essential to focus critically on the most important part of the subject, as elements that are even a millimetre closer or farther from the focal plane might be noticeably blurred. Due to this, the use of a microscope stage is highly recommended for precise focus with large magnification such as photographing skin cells. Alternatively, more shots of the same subject can be made with slightly different focusing lengths and joined afterwards with specialized focus stacking software which picks out the sharpest parts of every image, artificially increasing depth of field.
Compact digital cameras and small-sensor bridge cameras have an incidental advantage in macro photography due to their inherently deeper depth of field. For instance, some popular bridge cameras produce the equivalent magnification of a 420 mm lens on 35-mm format but only use a lens of actual focal length 89 mm (1/1.8″-type CCD) or 72 mm (1/2.5″-type CCD). (See crop factor.) Since depth of field appears to decrease with the actual focal length of the lens, not the equivalent focal length, these bridge cameras can achieve the magnification of a 420 mm lens with the greater depth of field of a much shorter lens. High-quality auxiliary close-up lenses can be used to achieve the needed close focus; they function identically to reading glasses. This effect makes it possible to achieve very high quality macrophotographs with relatively inexpensive equipment, since auxiliary closeup lenses are cheaper than dedicated SLR macro lenses.
[edit] Lighting
The problem of sufficiently and evenly lighting the subject can be difficult to overcome. Some cameras can focus on subjects so close that they touch the front of the lens. It is impossible to place a light between the camera and a subject that close, making extreme close-up photography impractical. A normal-focal-length macro lens (50 mm on a 35 mm camera) can focus so close that lighting remains difficult. To avoid this problem, many photographers use telephoto macro lenses, typically with focal lengths from about 100 to 200 mm. These are popular as they permit sufficient distance for lighting between the camera and the subject.
Ring flashes, with flash tubes arranged in a circle around the front of the lens, can be helpful in lighting at close distances. Ring lights have emerged, using white LEDs to provide a continuous light source for macrophotography.
Homemade flash diffusers made out of white Styrofoam or plastic attached to a camera's built-in flash can also yield surprisingly good results by diffusing and softening the light, eliminating specular reflections and providing more even lighting.
[edit] See also
[edit] References
- ^ macrophotography (n.), in New Oxford American Dictionary
[edit] External links
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Wikimedia Commons has media related to: Macro photography |
- Close Up and Macro Photography
- Macro Lenses — Special lenses for close-up work.
- Use of Microscope Stage for Microphotography
- Photo.net how-to — Guide to macro photography
- Make your own reversing ring out of a Pringles can by Haje Jan Kamps
- Information on inverted lenses
- Macro Photography Tutorial
- Insects-macrophotography Photos of insects
- Inexpensive Macro Photography DSLR with Manual Focus Lens
- Macro Photography Tips
