Table of content:
- About macro photography
- Macro photography gear
- Other equipment and techniques
- Technical considerations
Macro photography is a close-up type of photography, usually of very small subjects and living organisms. Ideally lenses takes pictures in a lifesize ratio of 1:1. By using various techniques, that I will explain in this article, it's fairly easy to achieve greater magnification than this. Relatively easy I can get 4:1 magnification, but equipment exist that lets you have even greater magnification.
Macro photography gear
In this part of the article I will describe various gear you can use for macro photography.
Intermediate rings or extension tubes
Extending the distance between the lens and the film or sensor, by inserting either extension tubes or intermediate rings between the camera body and lens. 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 shorten the available maximum focus distance and make it impossible to focus to infinity.
Bellows
Bellows basically does the same as the above extension rings, but is more flexible as you can adjust the distance between the lens and the camera house on the fly. This is my preffered method for macto photography.
Reverse lens
Ordinary lenses can be used for macro photography by using a "reversing ring". This ring attaches to the filter thread on the front of a lens and makes it possible to attach a second 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 especially 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 optimised for small reproduction ratios, reversing the lens allows it to be used for high ratios.
Placing an auxiliary close-up lens (or close-up "filter") in front of the camera's lens is one option. Inexpensive screw-in or slip-on attachments provide close focusing. 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. 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.
Other equipment and techniques
Macro lenses specifically designed for close-up work, with a long barrel for close focusing and optimised for high reproduction ratios, are one of the most common tools for macro photography. Most modern macro lenses can focus continuously to infinity as well and can provide excellent optical quality for normal photography. True macro lenses can achieve higher magnification than life size, enabling photography of the structure of small insect eyes, snowflakes, and other minuscule objects.
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.
Macro photography can also be carried out by attaching a camera to one optical path of a binocular microscope (stereo microscope), making use of the optics of that instrument as the imaging lens for the system. Between approximately 1976 and 1993, the manufacturers Wild Heerbrugg and subsequently, Leica Microsystems offered a dedicated microscopy system for macro photography, the macroscope line, with improved optical performance for photography at the expense of the stereo imaging facility of the stereo microscope; this system came with a range of dedicated stands, objective and supplementary lenses, and illumination systems. Following its discontinuation in 1993, Leica continues to offer similar products under the names Z6 APO and Z16 APO.
Technical considerations
Depth of field (DOF)
Housefly on a leaf photographed with a shallow depth of field, noticeable in the blurring in the foreground and the fly's right wing. Limited depth of field is an important consideration in macro photography. 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), preferably a ring flash is often used (see Lighting section).
Like conventional lenses, macro lenses need light, and ideally would provide similar f/# to conventional lenses to provide similar exposure times. Macro lenses also have similar focal lengths, so the entrance pupil diameter is comparable to that of conventional lenses. Because they focus at close subjects, the cone of light from a subject point to the entrance pupil is relatively obtuse (a relatively high subject numerical aperture, to use a microscopy term), making the depth of field extraordinarily small. 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.
The high magnification you may get during macro photography could make you only get parts of your motive in focus. It is possible to use a macro focusing rail to move your camera around to get everything in focus. Using a macro focusing rain you can get lots of pictures of the subject with slightly different focusing lengths and joined afterwards with focus stacking software which picks out the sharpest parts of every image. I like to use Adobe Lightroom for doing this, but other software has similar functionality.
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 difficult to place a light between the camera and a subject that close, making extreme close-up photography impractical. A normal-focal-length macro lens 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 can be helpful in lighting at close distances. Ring lights have emerged, using white LEDs to provide a continuous light source for macro photography, however they are not as bright as a ring flash and the white balance is very cool.
Good results can also be obtained by using a flash diffuser. 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.
Chromatic aberration
Many macro lenses are characterised by a high amount of chromatic aberration, especially when using reversed-lens, extension tube or close-up lens. Some macro lenses, called apochromatic lenses, are designed to better control this.