SHOP WINDOW -- AUGUST

TELE-CONVERTERS

HEAD

CLOSER ENCOUNTERS

INTRO

Camcorder zoom lenses sometimes need a little help. We've been taking a close-up look at some of the teleconverters now on the market in this month's Shop Window feature

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Camcorder zoom lenses have been getting steadily more powerful; not so long ago 6x magnification was the norm, but even now, with most machines having 8x zooms there are still times when you want to get that little bit closer to your subject. The simple answer is to screw on a teleconverter lens, there's one to fit just about every make and type of camcorder, ranging in price from under £30 to almost £300. Magnification factors extend from 1.5x to 5x but for most users the 2x teleconverter is the most convenient size, effectively doubling the power of the camcorder's own zoom lens.

Teleconverters fit on to the camcorder lens's filter thread; this screw fitting varies in size from 27mm, for the smallest palmcorders, up to 55mm on larger machines. It is important to choose the right size for your machine,  but most teleconverters come with a set of step-up or step-down rings, to fit lenses either side of the nominal thread size.

The autofocus systems on some camcorders can be affected by converter lenses, so be aware that you will almost certainly have to resort to manual focus. In order to avoid vignetting (shading in the corners) it is usually necessary  to set the camcorder's zoom to maximum magnification. Most of the larger teleconverters are too heavy to allow front-focus AS systems to work properly, even the smaller one can cause problems. It's important to make sure any screw-on lens fits your machine, without fouling the microphone, AF window or the  remote control and white balance sensors. Exposure systems can also be affected as the amount of light entering the lens is reduced, this may also cause vignetting at low light levels. For this reason teleconverters are best suited to outdoor shots, in good light. In all cases you will need a good quality tripod as the extra magnification and narrower depth of field will accentuate any camera shake. All of the accessory lenses we've looked at come with some sort of carry case or pouch, though the quality varies quite significantly.

The optical quality of these lenses is generally very high and such aberrations as there are unlikely to show up on video recordings made on normal 8mm and VHS-C machines. Owners of high-band equipment may feel there is a case for paying for better quality lenses, though unless the lens is going to be used all the time medium quality lenses should be quite sufficient.

Space is limited so we've only been able to cover a proportion of the teleconverter lenses on the market in any detail; we couldn't include multi-lens kits, for instance, or variable-magnification zoom lenses, and in the cases of some of the more prolific manufacturer we've limited our comments  to representative samples within their range.