Last summer I bought a Nikon teleconverter, the Nikon TC20 III. A teleconverter is a secondary lens that is mounted between the camera and the lens. This increases the distance between the camera’s sensor and the lens, increasing the focal length. The Nikon TC 20 III doubles the focal length of the lens, turning a 70-200 mm lens into a 140-400 mm lens!
Lenses are not cheap, especially quality glass comes with a high price. A new Nikon 70-200 f2.8 II costs €2.500 (and $2.500 in the USA), and buying a Nikon 200-400 f4 leaves a hole of €8.000 in your wallet! So what do you do when you own a quality telelens, and don’t have the money for a longer lens? Right, buy a €500 teleconverter!
There are three common converters available:
- a 1,4 converter to multiply the focal length by 1,4. So a 70-200 lens becomes a 98-280 lens.
- a 1,7 converter to turn a 70-200 lens into a 119-340, because it’s multiplied by 1,7.
- a 2,0 converter, to double the focal length.
At point of writing, both of the Nikon 1,4 and Nikon 2,0 converters have a third generation available (recognisable by the “III” in the name). The higher the generation, the better the quality. But there is a downside: adding more glass between your lens and camera reduces image sharpness. Theoretically, the 1,4 converter has less quality loss than the 1,7 or 2,0 version. However, because there is only a second generation of the TC17 and a third generation of the TC20, the quality loss between these two versions is not shocking.
There is a little catch when it comes to the focal length however. Some telelenses are prone to so called “focal length creep”. This happens while focusing on subjects close to the lens. If for example you have set your lens to 200 mm and you focus on a subject 2 meters away, internally the lenses shift to get the subject in focus. The positioning of the glass internally sometimes means that the focal length is readjusted to for example 190 mm. This is no problem for me, but be aware of this!
There is another catch to using a TC: Not only do they multiply the focal length, but also the maximum aperture (this is the largest aperture, or the smallest number on your camera). With the TC20, a Nikon 70-200 f2.8 lens turns into a 140-400 f5.6 lens. That is the reason why not every lens is suitable for using a teleconverter. The most sensitive focal point in your camera (usual the one in the middle) supports only apertures up to f8 in the most comon cameras. Any smaller aperture reduces the precision of the autofocus system. So a 200mm f4 lens, turns into a 400mm f8 lens using the TC20, making the autofocus system less reliable. Also, the best quality is reached by stopping the combination down by one stop, meaning that you lose even more light.
This is also the reason that with a teleconverter, the autofocus system becomes slower. If speed is necessary, like in sports, consider not buying a teleconverter, and rather look for a quality used lens.
And finally, keep in mind, that not only the teleconverter reduces the sharpness in your photos. Increasing the distance between you and your subject does too! Atmospheric disturbance is to blame for this. Dust in the air, or the heat rising up from the planet (like the heat waves rising up from the tarmac street during a hot day) breaks light in a for photography not flattering way. So, even on a cold day, you simply cannot expect to get a subject tag sharp if it is a hundred meters away from you. Don’t be fooled by thinking you don’t need to get close to a bird that you want to photograph, because you need!
So how is the Nikon TC20 III? It is good! I use it on a Nikon D7100 combined with a Nikon 70-200 VR f2.8 II, and that is a great combination. Even though prime lenses work better with a teleconverter than zoom lenses, it is still impressive. I have accepted the fact that the autofocus system is slower, and that quality is reduced a bit, but still pretty good! It takes some time getting used to working with such a range! As birds fill up more space in your viewfinder, keeping track of them is a challenge, with less margin for error.
Using the Nikon TC20 III means that I don’t need to crop my images (much) anymore. So here is your choice: lose quality (megapixels) by cropping, or by using the TC and don’t need to crop (as much) anymore! One word of advise though, do calibrate your lens and camera body regularly!
To summarise, here is why I like the Nikon TC20 III:
- Sharpness in combination with the 70-200 f2.8 VR III and the Nikon D7100 is pretty good!
- I don’t need to crop my images anymore
- No need to buy a new lens, this is a cheaper solution
- I am finally able to take a picture of that bird that won’t let me get closer than 10 meters
What you need to be aware of:
- A longer distance between you and your subject means sharpness reduction because of dust and mirage
- I need to stop my lens and TC down to f8 for optimal sharpness. Combined with fast shutter speeds to capture birds means that lots of light is needed for a good exposure
- It takes some time to get used to such a long focal lengths, 200mm or 400mm is a big difference!
- Your lens get’s heavier as a teleconverters weighs up to 500 grams
- Always attach the converter first to your lens, and than mount the combination to your camera.
For me the teleconverter is a good option, however, I don’t have a 400mm or larger lens to compare it with. After reading this review, do you thing a the TC20 III is an alternative to a big lens for you? Let me know in the comments!