A teleconverter is a small optical unit that fits between a lens and a camera body and increases the effective focal length. It is a handy way to gain reach, but it comes with trade-offs in light, focus speed and sometimes sharpness.
How It Works
Common teleconverters are described by a multiplier, such as 1.4x or 2x. A 1.4x unit makes a 300mm lens act like 420mm, and a 2x unit makes it act like 600mm. The multiplier also affects light.
- A 1.4x converter costs about one stop of light.
- A 2x converter costs about two stops.
- The maximum aperture becomes smaller by the same amount.
For example, an f/4 lens becomes roughly f/5.6 with a 1.4x unit, and f/8 with a 2x unit.
Effects on Focus and Quality
Smaller apertures can slow autofocus or stop it working on some bodies, which often have a limit on the smallest supported aperture. Check the camera maker’s guide for this limit before you buy.
Sharpness depends on the design of both the converter and the lens. Good pairings keep quality high; poor ones soften the image. Makers usually list which lenses are compatible, so follow their guidance.
Using One Step by Step
- Switch off the camera and remove the lens.
- Attach the converter to the body, then the lens to the converter.
- Switch on and check that autofocus and stabilisation work.
- Raise the shutter speed to account for greater magnification and shake.
- Use a support such as a monopod or tripod where possible.
Teleconverter or Crop?
| Option | Gain | Cost |
|---|---|---|
| Teleconverter | Full-sensor image with more reach | Less light, possible quality loss |
| Cropping in editing | No equipment change | Fewer pixels in the final picture |
| Longer lens | Best quality at that reach | Size, weight and cost |
Think about your subjects before buying. Birds in good light may suit a 1.4x unit very well, while a 2x unit on a modest zoom may leave you with a dim viewfinder and slow focus. Using a converter on a lens with a wide aperture keeps more light and works better than on a lens that is already slow. Consider renting a combination for a weekend to see whether the loss in speed and sharpness suits your type of shooting.
FAQ
Do teleconverters work with every lens?
No. Many fit only certain telephoto lenses, and some lenses have no room for them. Read the maker’s compatibility list.
Is a teleconverter good for wildlife?
It is popular for birds and distant animals, provided your lens remains bright enough to focus well in the light you have.
The Short Version
A teleconverter gives extra reach with a cost in light and sometimes sharpness. Choose one that your maker lists for your lens, expect to lose stops, and compare with simple cropping before you buy.
