Nikon TC-20E III Review

This is an in-depth review of the new Nikon TC-20E III teleconverter that was released in December of 2009, along with an updated version of the Nikon 300mm f/2.8G VR II lens. The Nikon TC-20E III is a major update to the existing Nikon TC-20E II teleconverter, sporting a brand new optical design with an aspherical element, which delivers better performance with many specialty telephoto lenses.

The purpose of teleconverters is to increase the focal length of lenses, in other words to get closer to subjects, and the TC-20E III is the biggest and the longest teleconverter manufactured by Nikon – it doubles the focal length of a lens. While this teleconverter works with any professional Nikon lens that can take teleconverters, it is specifically designed to work with fast prime lenses with an aperture of f/2.8 and larger. The Nikon TC-20E III is targeted at sports, wildlife and other types of telephoto photography where the photographer cannot physically approach subjects.

It was not easy to obtain the Nikon TC-20E III because of high demand/short supply and after waiting for a few weeks, I decided to just rent it for a couple of weeks instead. My objective was to try the Nikon TC-20E III specifically with the Nikon 300mm f/2.8G VR II and with the Nikon 70-200mm f/2.8G VR II to see how it truly performs in an outdoor environment when photographing nature. It is one thing to shoot test charts with a lens sitting on a tripod, and another to get out and do some real shooting.

Some lenses look great on paper and on test charts, but cannot perform equally well when used in an outdoor environment, especially with fast-moving subjects like birds. The primary reason is autofocus, the performance of which depends on many different factors. Teleconverters generally negatively impact autofocus performance, due to a considerable loss of light and contrast and the 2x TC is the worst in this regard. Adding a teleconverter slows down lenses and the Nikon TC-20E III slows down by two full stops. What this means, is that when the teleconverter is mounted on an f/2.8 lens, it slows down to f/5.6 and as you may know, autofocus performance on small apertures beyond f/5.6 is unreliable even in broad daylight conditions. Nikon clearly points out that autofocus does not work beyond f/5.6, so if you have an f/4.0 lens, forget about autofocus – you will have to resort to manual focus.

In addition, due to the considerable number of additional glass elements, the lens sharpness performance can suffer significantly, depending on the quality of the lens. While lenses like Nikon 200mm f/2G VR II, Nikon 300mm f/2.8G VR II and Nikon 400mm f/2.8G VR work great with 2x teleconverters, some lenses like the Nikon 70-200mm have been known to perform very poorly with any teleconverters longer than 1.4x. As I have demonstrated in this review, the new Nikon 70-200mm f/2.8G VR II works beautifully with the Nikon TC-20E III when stopped down a little, which was a nice surprise. Let’s take a closer look at the teleconverter.

Nikon TC-20E III Specifications

Detailed specifications for the lens, along with MTF charts and other useful data can be found in our lens database.

Nikon TC-20E III compatibility and performance chart:

The lenses with f/11 for both “Acceptable” and “Optimal” sharpness produce very unreliable results.

Lens Construction and Handling

Similar to other Nikon teleconverters and its predecessor, the Nikon TC-20E III has a rugged all-metal exterior and a metal mount that is built to last a lifetime. The solid construction, along with a whopping 7 elements make it one heavy teleconverter, weighing a total of 330 grams without a lens attached. As a comparison, the Nikon 50mm f/1.4G lens weighs only 280 grams. The Nikon TC-14E II and TC-17-E II weigh 200 and 250 grams, respectively. While the number of optical elements has not changed between the new and the older 2x teleconverters, two key differences to note are the redesigned layout/lens groupings and replacement of a regular lens element with an aspherical one. The aspherical element was added to improve image quality by increasing sharpness, decreasing coma and other aberrations. Like other teleconverters, the Nikon TC-20E III has fixed lens elements that do not move when focus ring or zoom ring are touched on the lens. This means that the lens is protected very well against dust and moisture.

Autofocus Speed and Accuracy

When it comes to autofocus performance, the Nikon 2x teleconverters have always been the worst (when compared to other Nikon teleconverters), since they slow down lenses by two full stops and degrade image quality. The quality of light that reaches the autofocus sensor is often poor and only large aperture lenses that pass through lots of light can focus well enough with the TC-20E III. For example, the Nikon 200mm f/2.0 works very well with the TC-20E III and autofocus is often both fast and accurate. Slower f/2.8 prime lenses are a little worse, but still accurate enough in bright conditions. As lighting conditions worsen, the autofocus performance gets less accurate and lenses might start “hunting” – that’s when the lens goes from infinity to close focus, unable to stop at a particular focus mark.

When the TC-20E III is used with slow f/4 aperture lenses, autofocus stops working completely or becomes extremely unreliable. With the exception of the new Nikon 70-200mm f/2.8G VR II, zoom lenses also start acting up in daylight with very mixed results. The Nikon 70-200mm f/2.8G VR II works surprisingly well with the TC-20E III and I found the autofocus performance to be good in bright conditions, although the lens also works very well with the TC-14E II and TC-17E II teleconverters. The same cannot be said about the older 70-200mm f/2.8 lens – it is only known to work well with the TC-14E II. The above table chart outlines which lenses perform best at what aperture with the TC-20E III. When photographing sports, wildlife and other fast-action photography, you have to be extremely careful when using the TC-20E III.

Not only will it take some time to get used to, but you also need to know how to get the best out of your autofocus system on the camera. For example, choosing anything but the center focus point will often result in focus hunting and you might need to manually pre-focus the lens before trying to acquire focus on your subject. In addition, using the focus limiter switch on telephoto lenses also helps, as lenses do not have to go through the full cycle of focusing back and forth. So if you are frustrated with the TC-20E III, I recommend taking your time and experimenting with the AF system on your camera. It goes without saying that AF performance will suffer even more on lower-end DX cameras, so I suggest using the TC-20E III on pro-level bodies like Nikon D300s and above.