Using The Canon EF 100-400 f/4.5-5.6 L IS II With a 1.4x Extender – You Won’t Believe This!

I’m currently shooting in the Canadian Rockies again and wildlife is all around me. Whilst I have my big Canon 200-400mm with me, I’ve mainly been shooting with the Canon 7D Mark II and the amazing Canon 100-400 f/4.5-5.6 L IS II. This combination get’s me to a 640mm equivalent field of view in a hand-holdable package. In the right light, the image quality is every bit as good as the $12,000+ 200-400mm lens (my Canon 200-400mm review). Yep, you read that right… let’s take a look.

I was curious what the performance of this lens would be like with a 1.4x extender. This combination gives you an equivalent field of view to an 896mm lens, and a minimum f/8 aperture. When I first tried this, and looked at the photos, my eyes popped out of my head! Even wide open at f/8, this is a more than useable combination. In fact, it’s sharper than my old Mk1 300mm f/2.8 IS with a 1.4x extender on it. These kinds of results have rapidly made this lens an all-time favourite from Canon.

I know that a lot of people aren’t going to believe me when I say this this combination is this good, so I’m including some images, with 100% crops. These images only have the default sharpening from Lightroom applied to them and they were all shot with the 7D Mark II. Now, this camera is VERY good, but it doesn’t resolve fine details like a full frame camera does. Had I taken these shots with my 5D, or a 1D, these would have been even sharper!

Considering these were both taken handheld, at close to 900mm out of a car window, I think this is astonishing performance! Every Canon wildlife photographer should have this lens in their arsenal. It is very rare that I say things like that so definitively, but this is a truly outstanding lens. Of course to get great results, you must understand the best ways to use an extender. This is a topic that has been covered extensively in my ultimate guide to extenders/teleconverters.

I wonder how the new RF mount 100-500mm performs…

Canon 100-400 II + 1.4x Extender – Example 1

Canon 100-400 II + 1.4x Extender – Example 2

Will Your Camera AF at f/8?

Not sure if you will be able to maintain AF with your camera, and the combination of the 100-400 + extender? Since this is a question that was asked so often in the comments, I have created a resournce to list all DSLR cameras that will maintain AF with a lens+extender combination that delivers a max aperture of f/8.

Photo of author
Professional photographer based in Yukon, Canada, and founder of Shutter Muse. His editorial work has been featured in publications all over the world, and his commercial clients include brands such as Nike, Apple, Adobe and Red Bull.

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18 thoughts on “Using The Canon EF 100-400 f/4.5-5.6 L IS II With a 1.4x Extender – You Won’t Believe This!”

  1. Thanks for the great article a quick questions if I may, what version of the 1.4x extender were you using I am guessing the version 3, I am looking at buying one second and am wondering if the price difference between the two is worth it.

    • I was using the III, yes. My understanding is that there was no optical difference between II and III. The difference comes with AF performance with Canon’s super-telephoto lenses. You are probably safe to buy the II if you want to save a few dollars.

  2. Dan,

    Getting ready for a Yellowstone trip in May. Last year I rented the Tamron 150-600 G2 and used my Canon 7D. I had decent results. However, I have been interested in the Canon 100-400 and the addition of the 1.4 extender, which is what brought me to your site. I currently have a Canon 70-200 IS lens and love it, but I need more reach.

    So, if you had your choice what setup would you use with the above options? The 100-400 or the Tamron 150-600. Personally I feel the Canon glass is superior to the Tamron as is the focusing. This question will help me also choose which lens to buy.

    I guess I just need to hear it from someone that has your experience.

    Thank you,

    • Yes, I think you will get better AF performance from the Canon glass, even when using the extender. I think, however, you will probably get very similar optical performance with the extender on the the 100-400. But with the “naked” 100-400, you will get far superior optical performance from the Canon.

      All this assumes you are talking about the Mark II version of the 100-400.

  3. Thanks for this writeup, Dan. You do mention the AF speed is reduced with the 1,4x, but there’s more to that. I recently was shooting wildlife with my Canon 5DSR, 100-400 II. I use servo AI and burst shutter mode with a grid of 9 AF points. All was fine until I added the 1.4x into the mix. Then the Servo AI focussing stopped working. The focus points no longer blinked when the subject was in the grid. Without that, I never knew if the camera was focussing on the subject. Very unnerving.

  4. Hello Dan

    Great post!
    What combo would you suggest for birding : 7D Mark II combined with canon lens 100-400mm and 1.4x extender or 7D Mark II with Tamron lens 150-600mm

  5. “7D Mark II. Now, this camera is VERY good, but it doesn’t resolve fine details like a full frame”

    Can you elaborate on this? Is this due (typically) increased relative pixel density in crop sensors exceeding lens ability to resolve, or something else?

    I’m using this on an M6 II. From the few shots I’ve taken so far, results are very good. Previously (with the 70-300L) I’d always felt a bit disappointed with sharpness, particularly feathers/fur, compared to what I’ve seen from friend’s Sony FF.

    I like crop for the size and “zoom”. How much difference is there really?


  6. Hi Dan,

    May I ask for your guidance. I have 500D Marl III and 100-400 II. I feel I am missing on reach for wildlife and wanted to go for a bigger range or extended. I have seen all the notes about the downside of the AF with the extender. Net net should I go for a Sigma/Tamron 150-600 or an extender of 1,4 or 2 with my existing 100-400. And what about the options I may have to go up to 800 lens, how much emphasis should I give to having something longer than 600..

    Many thanks

    • I would recommend going with one of the 150-600 options over using an extender on the 100-400. If you are lacking reach, that will be a better option.

      On a DSLR you have few options to go beyond 600mm, so I wouldn’t worry about that unless you plan to spend $15,000+ on the EF 800mm lens, which I would not recommend!

  7. Hi Dan, I appreciate your insights. Winter in Yellowstone next month. Canon 5d Mark IV body and currently have the canon 100-400 5.6 lens. Will I be better off with the 1.4 extender or should I think about the Tamron 150-600?

    • To clarify, do you have the Mk I or the Mk II version of the 100-400mm? There’s a big difference in performance with a teleconverter.


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