Tele-converters for Macro Photography
Tele-converters 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.
The Pro-Optic Multi-Coated 2x Tele-Converter, for example, is made with high quality multi-coated optical elements and is designed to operate electronically with the contacts that are built into your camera body. Designed specifically to be used with prime or zoom lenses of 100mm focal length or longer it didn’t seem to hurt image quality when I used it with two different 50mm lens but it’s always a good idea to follow the manufacturer’s recommendation if your interested in maximum performance and sharpness. All is not lost with slower lenses, and manual focusing is recommended when using a lens with a maximum aperture of f/4 or slower.
Having a tele-converter 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 Pro Optic 2X teleconverter. Exposure was 1/25 sec at f/14 and ISO 400 with a Canon ringlight used as light source. ©2011 Joe Farace
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 Pro-Optic multi-coated 1.4x tele-converter that will turn a 300mm lens into 420mm but only decrease the maximum lens aperture by one f/stop. Like its 2X sibling the Pro-Optic 1.4x tele-converter is designed for prime or zoom lenses of 100mm or above. Pro-Optic converters are available in Canon, Nikon, Sony (Maxxum) and Pentax mounts.
Having two tele-converters in your camera bags triples the number of focal lengths available and prices around $100 for each Pro-Optic converters represent an optical bargain.