Teleconverter Tip: Sometimes we push our lenses to the limit and they require a bit of assistance to get the shot we desire. A teleconverter can quickly become your best friend in such situations. A teleconverter allows you to increase the magnification of your telephoto or telephoto zoom lens by attaching to the end of the lens. A tele-converter can also be very useful in macro photography because it can enlarge the central part of the image captured by the primary lens.
We have a variety of tele-converters for every use and budget. Tele-converters are very popular additions to many photographer's kits, but they can come with a hidden price.
Adding tele-converter magnification can subtract camera automation. Most digital SLR's require a maximum open aperture of at least f/5.6 in order for autofocus and autoexposure to work properly. By adding a tele-converter behind a lens we decrease the amount of light entering the camera, essentially reducing the maximum aperture. A 2X converter on a standard 75-300 f/5.6 zoom lens reduces the maximum aperture to about f/11.0.
Tele-converters have been around for decades, they do the job as advertised. However be prepared to manually focus your camera's lens with a tele-converter mounted. Under bright, sunny conditions your camera may be able to achieve proper exposure readings, but under less than ideal conditions you will need either a hand held light meter or a workaround.
The easiest workaround is to take a meter reading through your camera before mounting the tele-converter. Make sure that the camera's exposure mode is set to Aperture (Av) and that the reduced aperture value of the lens plus converter are dialed in. Then after mounting the converter set the camera in Manual exposure mode and dial in your previous meter reading. As the light changes the photographer may have to take new readings to compensate.
Using a tele-converter is a balance between choices. On the one hand a tele-converter is much less expensive than a new, longer lens. On the other hand the cost savings comes at the expense of a little less reliance on camera automation.
Even with the loss of some automation tele-converters remain a popular digital camera lens accessory. As long as the photographer understands the limitations imposed, a tele-converter is a great way to expand the potential of anyone's lens kit.