Click Thumbnails to Enlarge

• 
• 
• 

Using a teleconverter

Techniques

24 October 2007 14:25

Teleconverters  are lens adapters that attach to the back of your lens to increase focal length. Sounds simple, but sadly there are drawbacks.

The converters made by the big lens manufacturers are matched to either a particular lens or range of lenses (usually the pro models) so you can’t just buy any one and expect it to work with all of your lenses.

There are a few cheaper models available, but even these are usually limited to lenses with maximum apertures wider than f/5.6. Part of the reason for this is that the converter reduces the maximum aperture of the lens by one or two stops, depending on the magnification. There’s also slight degradation of the image.

Pro lenses are higher quality and have larger maximum apertures so this doesn’t matter quite as much as on slower, cheaper lenses. For example: a 300mm f/2.8 telephoto lens with a 1.4x converter attached essentially becomes a 420mm f/4 lens, or a 600mm f/5.6 lens if you attach a 2x converter instead.

However, if you can only afford a cheaper 300mm f/5.6 lens, a 2x converter will give you a maximum aperture of f/11, making the lens much harder to use in all but the brightest conditions.