The Tiny World: Macro Magnification
Macro photography is the art of photographing small subjects at life-size or greater magnification. A true macro lens is capable of 1:1 magnification, meaning the image of the subject on the camera sensor is the same physical size as the subject itself. However, you can achieve macro-like results with standard lenses by using Extension Tubes.
How Extension Tubes Work
An extension tube is a hollow spacer that sits between the lens and the camera body. By moving the lens further from the sensor, you allow the lens to focus much closer than it was originally designed for, which increases the magnification of the subject.
The Formula
The magnification gain is a simple ratio of the extension length to the focal length of the lens.
New Magnification = (Extension / Focal Length) + Native Magnification
The Trade-offs of Extension
- Light Loss: As you extend the lens further from the sensor, the light has a longer distance to travel and is spread over a larger area. This results in an effective loss of light, often requiring a wider aperture or slower shutter speed.
- Focus Range: When using extension tubes, the lens loses the ability to focus at infinity. You can only focus on objects within a very narrow range close to the front of the lens.