This post is the first in a three part series looking at "What Is Macro". Through out the series we will examine macro photography from a technical, philosophical, and cultural perspective. In today's photography world there are a wide range of images that claim to be macro photographs. We'll take a look at a lot of images in this series but first lets start by understanding macro from a technical standpoint.
Macro is both a specific technical type of photography as well as an idea or concept. Photographically it is defined as an image with a reproduction ratio between 1:1 and 10:1. There is some debate about this definition, with some arguing the cut off is 5:1 but 10:1 seems to be the most cited number. A reproduction ratio of 1:1 means the subject is the same size on the camera sensor or film plane as in real life, for 10:1 the subject would be 10 times larger than actuality. Anything approaching 1:1 would be considered a close-up and anything after 10:1 falls into the realm of microscopy.
There are a range of different macro lenses by several different manufacturers capable of creating 1:1 images without the aid of accessories. But these lenses only get you to the very beginning threshold of macro photography. Canon has a lens designed only to produce images from 1:1 through 5:1, the MP-E 65mm. This lens has fixed focus points but is a joy to use once you get the hang of it.
In order to get magnifications greater than 1:1, with the one exception noted above, you are going need some additional gear. The most popular method is using extension tubes or bellows. Both of these tools are designed to do the same thing: create greater distance between the image plane and the glass elements in the lens.
There are additional methods for creating higher magnifications without adding distance between the camera and lens. The first is lens stack where you reverse mount a wide-angle lens to the front of a telephoto lens. Another is reversed lens, also generally done with wide-angle lenses. Here you reverse mount the lens directly to the camera body with the aid of a mounting adapter. Finally there are supplementary lenses you add to the front of a lens via the filter threads. There is incredible variation in quality among these lenses; many that I have tried left much to be desired. The Canon 500D filter however is an outstanding piece of glass and well worth the investment.
Back to the most used method of creating greater magnification, extension tubes. With this method the greater the distance between the lens and the image plane the greater the magnification you will achieve. Extension tubes can be stacked on top of one another to create a longer distance if desired. This is why they come in different lengths and are sometimes sold as sets. Macro lenses have the distance required for 1:1 magnification included as a part of their design. Since distance will produce greater magnification many lenses can be adapted to produce macro images this way.
The image above was taken with extension tubes on a macro lens creating a reproduction ratio greater than 1:1. Extension tubes used in conjunction with macro lenses give you the ability to produce higher magnification images.
Extremely narrow Depth of Field (DoF) is also one of the technically defining characteristics of macro photography. This occurs because the closer you get to your subject the more narrow your DoF will become. The Depth of Field in macro is often measured in millimeters or less. It is both a wonderful creative tool and a technically limiting factor at the same time. It requires precision in focusing and attention to detail to make the most out of it as a creative tool. Tools like focus stacking have been developed to give photographers greater DoF when doing this style of work.
Understanding the science and technology behind how macro photography is created allows macro craftsmen to constantly push the capabilities of what is possible. The drive to produce the images we see in our heads leads to great innovation, new techniques and new gear to execute them. There is a toolbox of techniques available to push beyond the limits of what has been possible thus far. Knowing the technical aspects of macro photography will help you produce the best images possible.