When to use teleconverters?
Friday, June 11, 2010 at 10:02AM 
Canon 1.4x II teleconverter
What is a teleconverter?
A teleconverter is an adapter that is used in between your lens and your camera, and they typically magnify your focal length by 1.4x or 2x. If you have a Nikon lens you will get the best quality with a Nikon teleconverter, and the same goes for Canon and other lens manufacturers. I am not a fan of off-brand manufacturers, such as Kenko.
- Canon makes 1.4x and 2x teleconverters
- Nikon makes 1.4x, 1.7x and 2x teleconverters
- Other manufacturers make 1.4x teleconverters at a minimum
A 300mm lens with a 2x teleconverter becomes a 600mm effective focal length. A 400mm with a 1.4x teleconverter becomes a 560mm.
Canon 2x II teleconverter
When you use a teleconverter, you also lose light coming into the lens. With a 1.4x you lose 1 f/stop of light, a 1.7x you lose 1.5 stops, and with a 2x you lose 2 stops. With a 300mm f/2.8 lens mated to a 1.4x teleconverter you end up with a 420mm f/4 lens.
Nikon 1.7x TC-17EII teleconverter
When do we use a teleconverter?
You will want to use a teleconverter when you would like to have more focal length.
What are the downsides to using a teleconverter?
Unless you are using the best glass on the market, you are likely losing optical quality. You are also losing 1 to 2 stops of light, so you will need to make sure that you can afford the light loss. I am often shooting at ISO 1600 and above at the end of the day, and I usually do not use a teleconverter when I am at the edge of my minimum shutter speed. Additionally, some cameras cannot autofocus when a lens is wide open at f/8. For example, for Canon shooters with a 500mm f/4 and a 2x teleconverter, you will be at f/8 as your wide open aperture, and on some cameras you cannot maintain autofocus with that configuration. A big down side, for sure. Canon 1-series cameras can maintain autofocus at f/8, however only with the center AF point.
Kenko 1.4x teleconverter
Which lenses can be used with a teleconverter?
A rule of thumb is that fast telephotos are the only lenses that you can use a teleconverter with, and zoom lenses will not work. There are exceptions, but not many. Here is a short list of lenses where you can use a teleconverter, and there are certainly more:
- 70-200mm f/2.8
- 70-200mm f/4
- 300mm f/2.8
- 300mm f/4
- 400mm f/4 DO
- 400mm f/2.8
- 200-400mm f/4
- 500mm f/4
- 600mm f/4
You technically can use a teleconverter on the popular 100-400mm, but please do not attempt it. Yes, technically it will fit together, however the optical quality absolutely sucks. Really sucks. I see this attempted all of the time, and I cannot emphasize strongly enough that it isn’t worth the effort.
I always travel with at least a 1.4 teleconverter for my longest telephoto lens, so it is an easy for me to gain more focal length without carrying more lenses and more weight.
Reader Comments (6)
Andy, I think that you answered all of my questions about teleconverters. I have a Kenko 1.4 which I have used for a nujmber of years. I am using it with a Nikon 70-200mm lens. Last week it shut down and would not autofocus when wide open on my Nikon D200. Later, I put the teleconverter on my D300 and it worked fine. Really though I think that it is time to upgrade to a Nikon teleconverter. I am considering the 1.7. I would be interested in hearing your thoughts about the new Nikon 2.0 teleconverter. I would also consider using the teleconverter with my Nikon 200-400mm. I am passionate about Africa photography. Your blog is great!
I think the Nikon 1.7x is closer to the 1.4x than the 2x in quality, however another thing to consider is the slower autofocus with the 1.7x and 2x teleconverters. On my 200-400mm f/4 I really only use the 1.4x, as I didn't like the 1.7x and 2x at all. Just my opinion.
Thanks. Your expertise is most appreciated.
Actually, you can use extenders with the 100-400 on 1-series bodies. Just to clarify.
True, but why would you ever want to use a teleconverter on a lens that is already optically challenged? The 100-400mm does not perform well until about f/11, and with a teleconverter you pretty much never get good performance at all. I make the argument that you are better off not using a teleconverter and crop when processing your images. You will end up with fewer, but better pixels. In my opinion there is never a situation to use the 100-400mm with a teleconverter. It just plain sucks, and the lens was not intended to be used with a TC in the first place.
Hi Andy,
Soon I will be going overseas to live in Zambia for two years and will have time to hone my wildlife photography skills.
I have been reading your website (thank you for your Safari DOF article) and thought you may be able to provide real advice - rather than the opinions thrown around on most forums.
I have a Canon 5DII and Canon 70-200L 2.8 IS (the original version) and will not be able to afford a new lens for this trip. I am really interested in your practical opinion of the Canon teleconverters with this setup in a wildlife park. It looks like you are quite comfortable shooting at relatively small apertures (f/11 - f/16) which it seems negates a lot of the criticism about teleconverters.
Am i crazy to consider using a Canon 2x on my lens for safari/wildlife photography?
Thanks,
Mike