Using Tele-Converters for Macro Photography
Teleconverters aka tele-extenders are small optical devices that fit between your camera body and lens producing greater magnification and increasing the lens’ focal length. A 2X extender doubles the focal length of the lens but there’s no free lunch. It also gobbles up light to the tune of two f/stops so the f/1.8 lens you attach to a 2X extender is now f/4. That’s not a bad trade but if you put it on a slower lens it can cause autofocus problems. Many AF systems require a maximum lens aperture of f/8 or less in order to effectively function. So be sure to the math before attaching a 2X extender to a smaller aperture zoom lens and be sure to read your camera manual, as painful as that may be.
Kenko’s Teleplus HD DGX 2x Teleconverter, for example, increases the range of Canon EF/EF-S lenses and supports communication between the lens and camera including metering, autofocus, and image stabilization. This model has enhanced EXIF data; to write equivalent focal length and aperture information.
Having a teleconverter is also useful for macro work because it magnifies the size of small objects, such as the above butterfly that was photographed using a Canon EF 50mm f/2.5 Compact Macro lens and 2X teleconverter. Exposure was 1/25 sec at f/14 and ISO 400 with a Canon ringlight used as light source.
There are times when you don’t need a 2x lens conversion and other times when you just can’t afford two stops of light loss. That’s when you need something like a Kenko Teleplus PRO 300 DGX 1.4x AF Teleconverter that will turn a 300mm lens into 420mm but only decrease the maximum lens aperture by one f/stop. Having two different teleconverters in your camera bags triples the number of focal lengths available and with affordable prices converters represent an optical bargain.