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Tips & Tricks

Teleconverters | Worth Your Money Or Not Worthwhile?

By Kishore Sawh on May 10th 2015


Do you understand teleconverters? I mean really understand how they work, which are the best ones, and what the drawbacks are?

I generally tip my hat to Tony Northrup, not particularly because of the type of images he creates, but because he has a very effective way of distilling and bringing across some complex information, and I appreciate that intelligence. His latest venture aims to clearly explain the often confusing world of teleconverters – a subject wildlife, sports, and aviation photographers will appreciate.

One of my passions is aviation, and the fact that photography comes second to that, meant I was always going to be interested in bringing the two together. But the game is expensive when it comes to equipment because you need big, fast lenses if you’re not shooting air-to-air. So when you want the reach, but it’s farther than your pocket is deep, teleconverters seem to be the answer. But which ones to get? Why would people pay for expensive long glass if teleconverters do the job? Which brands are good? What are the trade-offs? When you dive into this, you realize how deep a hole it is, and I wish I had this video when I began many years ago.


Tony explains that a teleconverter is essentially a magnifying glass element between the lens and camera, which spreads out the entire image circle, so a smaller portion of the circle fills the sensor, so it’s seeing a smaller part of the image coming from the lens – this is the magnifying effect. So you’re pulled closer, but gathering less total light. You’ll also likely have to use a higher ISO to use the same shutter speed, and keeping shutter speed high is important when using long focal lengths. This, as Tony explains, puts a lot of emphasis on the overall resolving power of the lens.

Most teleconverters are 1.4x or 2x converters, and to understand what that means for your imagery, you’ll need to multiply your focal length AND your aperture by either 1.4 or 2x. So an f/2.8 200mm lens with a 2x teleconverter would become 400mm f/5.6. That’s a huge jump in reach, but also a huge loss in light. It gets slightly even more tricky involving a little more math should you be using a crop sensor camera. Interestingly, and not something I thought of before, Tony mentions that in many cases using a crop sensor camera will give you better results with a teleconverter because there are more pixels in a smaller space, allowing for more detail through the center of the lens.


an old example shot taken with a 2x tele that gave me the reach, but poor quality.


[REWIND: The D750 Review | It’s Achilles, Less His Heel]

Something else he addresses is the possible penalty of losing autofocus. I’ll say now, that many teleconverters immediately render autofocus useless because they just weren’t built to work with it. You’ll find this in many third party versions, but even if they do, many AF systems will only work with lenses that have a minimum aperture of 5.6 or lower. So if you slap on even a 1.4x teleconverter with a lens with an aperture of 5.6, it becomes an f/8, which means the AF will often cease to function. This seems to be something that’s changing however, as new cameras like the D750, D810, D4s, 5D MK III, and 7D MK II all allow for f/8 AF (and many of you many know that Canon will only give you single center point AF like this).

There’s more that Tony explains in the video that’s both fascinating and useful, and most definitely worth a watch, or maybe two. You can find more from Tony here on his site and YouTube.

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A photographer and writer based in Miami, he can often be found at dog parks, and airports in London and Toronto. He is also a tremendous fan of flossing and the happiest guy around when the company’s good.

Q&A Discussions

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  1. Dragoș Ardeleanu

    I am so glad I found this article.
    I’m intending to use a 70-200mm f/2.8 from Canon with a x2 convertor to shoot concerts.

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    • Kishore Sawh

      You might have luck and it depends too if you’re shooting handheld or if you’ll have a spot to use a tripod. I would assume that in such low light, a 2x tele even with a 2.8 is going to require you to really up your ISO.

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  2. Chris Callahan

    There are many images I simply cannot get without a TC. Also, use of a TC requires VERY specific technique and care. The new TC’s are much better than the old ones… For me, TC’s are the only way to go. I am a bird photographer, as background for my thoughts.

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  3. Bruce Joseph

    Very informative and well done. Thank you.

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  4. Ed Rhodes

    tony always does good in-depth videos

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  5. Joe Sharp

    I agreed with every thing Tony said until Pentax came out with their HD 1.4 TC it is a game changer. I tried every TC I could find and was never happy with the detail, the pictures always had more detail without the TC. This new one on my DA* 300 or really any of my pro lenses brings you closer with no loss of detail! The other thing for those of us that plan on getting the full frame pentax when it come out this fall is the converter allows you to get a full frame image from a crop sensor lens. I have used this on my film camera to prove the concept and it works great.

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    • Thomas Horton

      “The other thing for those of us that plan on getting the full frame pentax when it come out this fall.

      I hope I hope I hope.

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  6. Thomas Horton

    Nothing is free when it comes to physics. There will always be a compromise when using a TC.

    It is up to the photographer to decide whether the negative compromises are worth the positive compromises.

    TCs suck or are a great boon… depending on the photographer and what is needed. :)

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  7. Jeff Forbes

    Tony Northrup’s photography may not be inspirationally good, but his communication skills are superb. He teaches technical concepts that go beyond the basics with a clarity that is unmatched.

    AKA I’m always happy when he does a video on something that hasn’t been covered a ton.

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  8. J D

    Very interesting. This was something I was very curious about as I am looking at purchasing one.

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  9. Lauchlan Toal

    Always neat to hear Tony’s thoughts on things. I haven’t had the chance to try teleconverters myself yet, but as far as I can tell he brings up a lot of good points. Thanks for sharing the video, Kishore.

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    • Kishore Sawh

      Lauchlan, (interesting name, by the way), Tony’s approach is generally very different than most educators out there, most of us here on SLRL included. He has some really brilliant videos and one of the few people out there whose work i have no problem recommending. Glad you like it

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