Teleconverters increase the effective focal length of a lens without increasing the minimum focusing distance. This means they can help bring you eyeball to eyeball with our feathery friends.
However, they do have one big drawback. They decrease the amount of light you have to work with by one to two stops. I use two teleconverters: the Nikon 1.4x and 2x.
These tele-converters are not fully compatible with all Nikon lenses and cameras. Before purchasing one, read the compatibility chart on Nikon’s web site carefully.
The compatibility issues fall into two big categories: physical incompatibilities and autofocus limitations.
Teleconverters sit between the camera and the lens. Some teleconverter/lens combinations won’t work because they bring the rear element of the lens into contact with the teleconverter. This could damage both pieces of equipment.
Other combinations reduce the amount of light so much that the autofocus no longer works properly. This typically happens when shooting at f8 or a smaller aperture.
Autofocus is critical when shooting birds in action. They just move too fast (at least for me) to pan with them, hold one finger on the shutter, and use the other hand to focus. This causes me to miss many shots.
However, there is hope. Read the footnotes in the compatibility chart carefully. When using the 2x, autofocus IS available with cameras that offer f/8 support. These include the Nikon D4, D800/D800E, D600 and D7100.
It took me a long time to find this footnote. I wish I would have seen it years earlier. With one of these cameras, you can use the 2x with any lens in Nikon’s range that is physically compatible. (Remember, if elements touch, you could scratch your lens and the teleconverter.)
So I can use the 2x with my D4, the 600mm f4, and the 200-400 f4 zoom and the 400 f2.8. The 2x turns the 600mm lens into a 1200mm lens and so forth. For reclusive and skittish birds, this extra “reach” can mean the difference between getting a great shot and missing it altogether.
Some people talk about using a camera like the D800 which has a 36 megapixel sensor and just cropping the image to obtain the desired magnification. While this is certainly a viable technique, its not the optimal technique in my opinion. The extra megapixels generate heat which creates noise. The images also take longer to download to the card which means you don’t get as many frames in a burst. And the frame rate on the camera when shooting in continuous mode is less than half of that of the D4.
If you want your kid to be into this kind of shooting, start a savings account today. There’s just no substitute for a great camera and fast glass. And it’s not cheap.