Macro Monday: Extension Tubes
Want to make photographs even closer than close-up filters let you capture? The next step up the macro-focusing ladder is accomplished by adding an extension tube to your existing lens. Extension tubes provide additional separation between your lens and camera’s imaging chip that’s required for close-up photography. You might think of them as an alternative to the more complex and expensive extension bellows some manufacturers offer as a close-up accessory.
Using extension tubes, I photographed the flower at left in my North facing kitchen window using a Canon EOS 20D and an EF 50mm f1.8 lens with a 21mm extension tube. A sheet of white paper was held on camera right during the exposure to provide fill. Exposure at ISO 200 in Aperture priority mode was 1/4 sec at f/16 to maximize depth-of-field.
An inexpensive extension tube set, such as Pro-Optics’ (below) includes three tubes of different lengths that can be used in individually or in combination to produce larger or smaller magnifications based on total extension length. These tubes couple with your camera metering mechanism and offer full auto focus compatibility. Pro-Optics’ extension tube set is available for Canon EOS and Nikon SLRs and includes three tubes (31mm,21mm & 13mm) which can be combined to obtain various magnifications and couple with your camera’s TTL metering and AE mechanisms.
Factoid: Extension tubes will reduce the amount of light falling on the sensor but your camera’s TTL metering system should automatically compensate for any light loss.