Tuesday, February 4, 2014

Extend Yourself

Yesterday’s blog mentioned teleconverters as a way to give your lenses more “reach,” enabling you to get tighter shots of birds and wildlife. So what are they and how do they work?

Basically a teleconverter is a small lens that goes between the main lens and the camera body, increasing the focal length of the main lens. In general there are two sizes  -  1.4x and 2x. The 1.4x increases your lens’ focal length by 40%, and the 2x doubles its focal length. So if you put a 1.4x on a 200mm lens, the effective focal length increases to 280mm. If you put a 2x on a 200mm lens, the effective focal length becomes 400mm.

While teleconverters are good tools, they do have some negative aspects. The 1.4x cuts light transmission by one stop, and the 2x by two stops. What does that mean? If normally your lens’ widest aperture is f/4, use of the 1.4x teleconverter will reduce that to f/5.6. If you use the 2x, your widest f/stop will be reduced to only f/8. This means that it will be best to use teleconverters on bright days when there is a lot of light to work with.

The other downside is that use of teleconverters can cause some degradation of the image, primarily with less expensive lenses. With higher-end lenses, the degradation is barely noticeable, but with other lenses you may see a significant loss of sharpness and detail.

Teleconverters may be used with zoom lenses, even though some manufacturers recommend against that.

Since they are essentially lenses, they tend to be expensive. But they are less expensive than buying a lens of the focal length that a teleconverter will create. And they can be used on a variety of lenses. The best ones are the ones made by your camera’s manufacturer. So Nikon teleconverters for Nikon bodies, Canon for Canon bodies, and so on.

There are other brands of teleconverters that tend to be less expensive, but they will certainly degrade the image greatly, and I do not recommend them.

So there’s the good news and the bad news. If you have relatively good lenses, but do not have a longer lens of your dreams, then consider getting a 1.4x teleconverter.  While the 2x will give you even more reach, I do not suggest one that large since it cuts so much light and will potentially degrade the image somewhat more than a 1.4x teleconverter.

To create today's image, I used a 1.4x teleconverter. Even so, it did not get me in as close as I wanted, and I had to resort to cropping after downloading it onto my computer to get this tight image of duck feathers.

Shutter Speed 1/640 sec.  Aperture f/7.1.  ISO 400.  Lens: Canon 200-400mm f/4L IS with 1.4x telextender for an effective focal length of 560mm.  Camera: Canon 5D Mark III.  Gitzo tripod with Really Right Stuff ballhead and Wimberley Sidekick.

TODAY’S QUOTE: “To the man who only has a hammer, everything he encounters begins to look like a nail.”  --Abraham Harold Maslow

No comments:

Post a Comment