The Benefits of Using Extension Tubes for Macro Photography
One of the best ways to turn an ordinary camera lens into a macro or close-up lens is to use an extension tube — a piece of equipment fixed in place between the lens and the camera body in order to create a greater space between the two. Extension tubes work as a middleman between the lens and the camera’s digital sensor, with their purpose being to hold the lens in place.
To achieve focus on a subject at a given distance, the lens has to be positioned at a certain distance from the camera’s digital sensor. If the distance of the subject changes, the distance between the lens and sensor has to change accordingly.
As you rotate the focusing ring on your lens (refer to your owner’s manual to locate the focusing ring), the lens itself moves backward and forward in relation to the digital sensor.
The farther the lens is from the sensor, the closer you can be to the subject and keep it in focus. The closer the lens is to the sensor, the farther you can be from the subject and keep it in focus. When you use the lens’s auto-focus feature, the camera rotates the focusing ring automatically to achieve focus.
100mm, 1/160, f/16, 100
The diagrams show an example of the subject-lens-digital sensor relationship. The camera on top is focused farther because the lens is closer to the sensor. The camera below is focused nearer because the lens is farther from the sensor.
If moving the lens farther from the camera’s digital sensor enables you to achieve focus on closer subjects, then it only makes sense that creating a greater distance between the two by using an extension tube enables you to get much closer to subjects with an ordinary lens. This figure compares the focusing abilities of a lens with and without an extension tube attached.