Subscribe Now!

Customer Service

GADGET BAG

Teleconverters

Increase the focal length of your telephoto lenses

By Ibarionex R. Perello

A teleconverter offers photographers the means to shoot at increased telephoto focal lengths without buying a completely new lens. With 400mm and higher lenses costing thousands of dollars, an optical accessory that delivers an increased focal length at a fraction of the cost has its obvious appeal.

With magnification factors typically ranging from 1.4x to 2x, teleconverters increase the effective focal length of a lens. Modern teleconverters include high-quality optics and coatings that ensure sharpness, less flare and reduced optical aberrations when combined with a telephoto. Attach a 2x teleconverter to a 300mm lens and you have the equivalent of a 600mm lens.

A teleconverter (also called a tele-extender, converter or extender) is an optical device that fits between your camera and the lens. It optically magnifies a lens’ focal length. Most of today’s teleconverters include electronic contacts that maintain numerous camera/lens functions, including autofocus, metering and special functions such as vibration control. The lack of such contacts results in the loss of autofocus and limits the use of exposure modes, leaving you with the option of manual mode.

Teleconverters are typically designed to work with specific lenses, primarily those with fixed focal lengths. Teleconverters are also optimized for lenses of a certain range, such as 200mm and below or 300mm and higher. Performance suffers otherwise. In some cases, there are physical obstructions incorporated in the converter and lens design that prevent the converter from being used with an incompatible lens. Check lens compatibility when considering any teleconverter.

The cost to be paid for the magnification a teleconverter provides is light loss. A 1.4x teleconverter results in a light loss of one stop, and a 2x teleconverter reduces the light reaching the sensor by two stops. So a 300mm ƒ/2.8 lens is transformed into a 420mm ƒ/4 with a 1.4x teleconverter and 600mm ƒ/5.6 with a 2x.

Although the light loss might seem a disadvantage, the benefits of having the increased focal length in the field can mean the difference between getting and not getting the shot. With today’s digital cameras, it’s an easy matter to increase the ISO sensitivity of the camera to compensate for the effective light loss.

Light loss is a problem for many variable-aperture zoom lenses. Attach a 1.4x teleconverter to a lens with a variable maximum aperture of ƒ/4-5.6, and your effective aperture becomes ƒ/5.6-8. This typically results in the loss of autofocus function, as most AF systems require a minimum light level of ƒ/5.6 to be consistently effective. Though there are fast zoom lenses that can be used with teleconverters, you generally can achieve better quality when using a converter with a fixed-focal-length lens. read more»

PAST GADGETS

Gadget Bag: The Long View
May 2007
Compact super-zoom cameras offer tremendous telephotos in portable packages
By William Sawalich

Gadget Bag: Multimedia Storage Viewers
April 2007
Back up and review your images in the field with handheld media devices
By Jon Sienkiewicz

Gadget Bag: Stocking Stuffers
December 2006
Discover how some affordable accessories can fill a holiday niche
By Ibarionex R. Perello

Gadget Bag: Have A Ballhead!
August 2006
Prized for solid construction and ease of use, ballheads are the choice of professional landscape photographers the world over
By Ted Alan Stedman

Gadget Bag: Batteries
June 2006
What you need to know for reliable power in the field
By Jon Sienkiewicz

Gadget Bag: Camera Gear Backpacks
July 2006
Making your load lighter in the field
By Jon Sienkiewicz

Gadget Bag: Teleconverters
April 2006
Increase the focal length of your telephoto lenses
By Ibarionex R. Perello

Gadget Bag: Sharpness Is Easy
May 2006
Tripods are indispensable, and new, exotic materials and construction make them better, lighter and stronger than ever
By Jon Sienkiewicz

Gadget Bag: Have Tripod, Will Travel
March 2007
Take along a tripod when away from home to ensure sharp photographs
By Ibarionex R. Perello

Gadget Bag: Weather Tamers
January/February 2007
Dramatic weather makes for dramatic photos, but you need to protect your camera for the conditions
By Jon Sienkiewicz

Gadget Bag: Rolling, Rolling, Rolling...
November 2006
Bring your digital darkroom with you on your next photo adventure
By Jon Sienkiewicz

Gadget Bag: Take It In Wide
November 2005
Expand your image-making possibilities with a wide-angle lens
By Maura C. Lanahan

Gadget Bag: Wireless Tools For The Outdoor Photographer
December 2005
New technologies cut the cables and give us expanded creative options
By Wes Pitts

Gadget Bag: Light Up Your Life
September 2005
Flash accessories and lighting concepts to help enhance your photography
By Maura C. Lanahan

Gadget Bag: Steady Sidekicks
October 2005
Accessories to enhance the performance of your tripod
By Maura C. Lanahan

Gadget Bag: Power Hungry
July 2005
Today's batteries help satisfy our insatiable electronic gear
By Ibarionex R. Perello

Check out our other photo sites: