Macro photography
Macro photography refers to close-up photography; the classical definition 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 4×6 inch (102×152 mm) print is made, the image is life-size or larger. This requires a magnification ratio of only approximately 1:4, more easily attainable by lens makers.
Equipment
There are several kinds of equipment for making the image the required size. These include
- Using a special-purpose lens called a macro lens (some manufacturers call it a micro), having a long barrel for close focusing. A macro lens might be optimized to provide its best performance at a magnification of 1:1. Some macro lenses, like the Canon MP-E 65 mm f/2.8, can achieve even better magnification— up to 5:1 macro, bringing the structure of small insect eyes, snowflakes, and other minuscule but detailed objects into striking focus. However, it is more common for a photographer to use a "standard" ( 1:1 ) macro lens, like the Canon EF 100mm f/2.8 Macro USM
- There are different categories of macro lenses, depending on the focal length
- 50-60mm range typically used for product photography and small objects
- 90-105mm range the standard focal range used for insects, flowers, small objects
- 150-200mm range gives more working distance - typically used for insects and small animals
- a few zooms provide a macro options, but they generally do not allow a 1:1 magnification
- Placing an extension tube between the camera body and the lens. The tube has no glass in it; its sole purpose is to move the lens farther from the film or digital sensor. The farther the lens is from the film or sensor, the closer the focusing distance (and the greater the magnification) and the darker the image. Tubes of various lengths can be stacked together, allowing for increasing levels of magnification while simultaneously decreasing working distance. With tubes attached, the camera will often lose the ability to focus to infinity.
- Using a bellows attachment between the camera body and the lens to extend the lens to film plane distance. Similar to an extension tube, but adjustable.
- Placing an auxiliary close-up lens in front of the camera's taking lens. Inexpensive screw-in or slip-on attachments provide close focusing at very low cost. The quality is variable, with some two-element versions being excellent. This method works with cameras that have built-in lenses. 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.
- Attaching a telephoto extender between the camera body and the lens. A 1.4× or 2× teleconverter gives a larger image, adding macro capabilities. As with an extension tube, less light will reach the film or sensor, and a longer exposure time will be needed. However, working distance remains the same as without the teleconverter.
- Using a smaller film or sensor. Placing a rollfilm adaptor on a 4×5 view camera can give a macro image. Likewise, using a digital camera with a cropped sensor will yield the appearance of more magnification. Enlarging a small portion of a 35 mm negative or slide also results in a larger image. Photographers might debate whether this is true macro photography, but it can result in a frame-filling photograph that is as large as the original subject.
- Reversing the lens using a "reversing ring". This special adapter 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 lifesize magnification using fairly cheap, "standard" (not specially designed for macro) lenses can be produced. For cameras with all-electronic communications between the lens and the camera body, such as Canon EOS, reversing rings are available which allow all camera functions, including open aperture metering, to be used. When used with extension tubes or bellows a relatively cheap but highly versatile macro system can be assembled.
- Reversing a lens of lesser focal length in front of a normally mounted lens using a very inexpensive "macro coupler," which uses two male filter threads to join lenses. This method allows most cameras to maintain the full function of electronic communication with the normally mounted lens for features such as open-aperture metering. Magnification ratio is calculated by dividing the focal length of the normally mounted lens by the focal length of the reversed lens (i.e., when a 50 mm lens is reverse mounted on a 200 mm lens a 4:1 magnification ratio is achieved). The use of automatic focus is not recommended due to the extra weight of the reverse-mounted lens. Attempted use of automatic focus with this technique could result in damage to the camera or lens. Working distance is significantly reduced as compared to the original lens.
Technical considerations
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 blurry. Due to this, the use of a microscope stage is highly recommended for precise focus with large magnification such as photographing skin cells.
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 piece of glass in the lens. It is impossible to place a light between the camera and a subject that close, making this 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. More recently, ring lights have emerged, using white LEDs to provide a continuous light source for macrophotography.
Examples
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Image:Hibiscus petal.jpg|Closeup of Hibiscus petal, a close-up photograph taken through Canon PowerShot A95
Image:Lice_macro.jpg|Colony of aphids on a stem. Macro photo taken using an inverse mounted lens on a Canon G3
Image:IMGP4550.JPG|close-up of a thumbnail on the Macro photography page, taken with a Pentax *ist DS and macro lens
Image:DSC_3541.JPG|Macro closeup of flying bug on finger. Nikon D50 with Sigma 105/F2.8 macro lens, 68mm extension tubes & Sigma EM-140 ring flash
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See also
- Wildlife photography
- Nature photography
- Cloudscape photography
- Landscape art
- Photography
- Photographs
External links