How to Stack Canon Extenders

UPDATED: Feb 28th 2017 – Note added about loss of infinity focus.

Firstly, if you aren’t familiar with the use of extenders, sometimes called teleconverters, I’d urge you to read my existing in-depth guide to using extenders for your photography. Extenders allow us to extend the focal length of compatible lenses, and they come in a variety of magnifications. For Canon lenses, they are available in 1.4x or 2x variations, and we’ll be focussing on extenders for Canon cameras in this particular article. Stacking extenders simply means using more than one of them simultaneously, and for Canon lenses the solution is quite simple. On the other hand, the solution for Nikon lenses is much more complicated and usually requires physical modification of the extenders with a metal file. Since I’m a Canon shooter, I can’t really demonstrate the Nikon method for you.

Why stack extenders?

The vast majority of people looking to stack extenders are wildlife photographers who want to fill more of their frame with their subject. Extenders, if used correctly, can be a great way to get more reach from your lens, and get smaller, cheaper lenses up to the kind of focal length that might otherwise cost you over $10,000 if you were to buy a prime lens version. For example, using a 1.4x extender on a Canon 100-400mm f/4.5-5.6 L IS II gives you a good quality 560mm lens that costs about $2600 for the combo, whereas a 600mm lens would cost you closer to $12,000.

The problem is that there will always be occasions when something is still too far away for you to compose the shot exactly as you’d like to. It doesn’t matter if you start with a 200mm, or if you’re lucky enough to have one of the big guns like a 600mm! There will always be times when you’d wish to be a little closer. This is when stacking extenders can be a solution.

Complications and considerations of stacking extenders

If you choose to go down this route there’s several things to consider before we even look at solving the problem of physically connecting the extenders. When you use a 1.4x extender it cuts the light entering your lens by 1 stop. When you use a 2x extender it cuts the light by 2 stops. When you stack extenders, you will lose the combined loss of light so if you stack a 1.4x and a 2x for example, you’ll lose 3 stops of light. If you stack 2 x 1.4x extenders, for a total magnification of 1.96x, you’ll lose 2 stops of light.

In many cases this means that you’ll lose the ability to autofocus, or vastly decrease its potential, depending on which camera you are using. A lot of cameras can’t autofocus a lens when its maximum aperture is f/8, although though some, like the Canon 7D Mark II and 5D Mark III will give you a single, central AF point at f/8 or the central point with 4 surrounding points. At the time of writing this article, only the Canon 1D X Mark II has the ability to deliver full autofocus with a lens which has a max f/8 aperture. Even if your camera does allow for some form of autofocus with your final lens+stacked extender combination, the AF speed will be vastly decreased. In other words, you probably don’t want to try stacking extenders whilst shooting fast moving subjects like birds in flight, or race cars on a track.

The next consideration is that extenders do degrade the sharpness of a lens and add vignetting to the image at wider apertures, particularly when stacked. Your images will benefit from having the lens stopped down some way from the maximum aperture, but of course this eats up even more of your light which has to be compensated for by shutter speed or ISO. Long story a little bit shorter, you’ll probably find it hard to get a fast shutter speed with a stacked set of extenders, unless you are outside in the midday sun, so be prepared to choose your subject wisely, or crank up your ISO to a very high value even in daylight.

Infinity Focus Loss

Any time you use an extension tube, you will lose the ability to focus to infinity, so the same goes for including one in a stack between two extenders. Whether or not this will make a difference to you is dependant on the lens that you are using, and also what kind of subject you are trying to shoot. I would hazard a guess that most people are stacking extenders to use on telephoto and super telephoto lenses to get “closer” to wildlife. I can’t speak for every situation, but this one seems the most relevant. Many of Canon’s super telephoto lenses are actually designed to focus past infinity, so the inclusion of an extension tube actually just brings the whole thing back roughly around the infinity mark. As an example, I stacked a 1.4x and a 2x extender on my Canon 400mm f/4 DO II, and pointed it down my street.  I was easily able to focus on the house at the end of my street, which was some 150-200ft away. In other words, whilst it might cause you to lose the ability to focus on an object on the horizon, I doubt that is what most people are trying to do with such lenses. Wildlife is typically MUCH closer than the house at the end of my street, so the loss of infinity focus makes no practical difference to me at all. Every lens will be slightly different, and please feel free to share your own combinations in the comments below, but my gut says that this won’t be a problem for most people.

Stacking extenders with an extension tube

how-to-stack-extenders

The design of Canon’s extenders means that you can’t directly couple two extenders together because the protruding glass element physically doesn’t fit. The way to get around this is to use a 12mm extension tube between the two extenders. If you aren’t familiar with extension tubes, take a look at my previous in-depth guide to extension tubes for lenses.

No optics in an extension tube!
No optics in an extension tube!
Here you can see exactly why the extension tube is necessary. The protrusion from one extender would otherwise easily touch against the rear element of the other one, preventing them from coupling.
Here you can see exactly why the extension tube is necessary. The protrusion from one extender would otherwise easily touch against the rear element of the other one, preventing them from coupling.

An extension tubes looks a lot like an extender, but it doesn’t actually have any glass it in it at all. Its usual purpose is to alter the minimum focus distance of a lens by shifting it further away from the camera’s sensor. For the the purpose of coupling two extenders together though, it perfectly moves the protruding element just far enough away that two canon extenders can be stacked.

It’s worth noting that extenders can be purchased at various heights. Canon make a 12mm and a 25mm, but there are third-party versions in a variety of other sizes. For the purposes of stacking two Canon extenders together, you only need a 12mm extension tube, and this is what I would recommend that you use. Whilst extenders don’t alter the sharpness of an image, they do introduce a little vignetting and that increases the higher the extension tube you use. For this reason, if you have the choice, you should use the smallest extension tube you can for your stacking, which is the 12mm. Personally I use the Canon 12mm, but there are lots of good value third-party ones as well. The most commonly used third-party extension tubes are the Kenko tubes, and I’ve previously written a comparison between the Canon and Kenko extension tubes which you might want to check out as well.

Extenders that don’t need extension tubes to stack

Canon’s own Mark III extenders will need the extension tube in order to stack them together as we have seen, but some third-part extenders will stack together without using the intermediary extension tube. I’m a little loathe to state categorically that this can be done since I’ve not tried it myself, but it is widely reported that you can stack a Sigma EF 1.4x extender and a Sigma EF 2x extender together with no tube between them. I have also seen the same reported for Kenko extenders. I would say that if you plan to do this, make sure you either try it in a store first, have a store salesperson try it for you, or buy it from a place with a very good return policy like B&H Photo, just in case it doesn’t work as expected. I’d also caution that generally these third party extenders are thought to be good, but not as good as the Canon ones in terms of image quality. Since stacking extenders already puts a huge strain on image quality, if the results are very important to you then it would be best to use the highest quality extenders you can get, which are the proper Canon ones.

UPDATE: It has been pointed out to me in the comments that Canon’s Mark II extenders did actually stack together without need for an extension tube since the rear element of the 2x was recessed some way. For many of Canon’s latest long zooms and super telephoto lenses, the newer Mark III extenders provide some AF function improvements, so I would still recommend those for most people. If you happen to already own a Mark II extender though, you may not need the tube. A Mark II 2x and a Mark III 1.4x can be stacked without an extension tube as well, according to several other 3rd party sources that I researched. I have not tried it myself, so wield some caution….

kenko-extender
You can see that the Kenko extenders lack the protruding element that features on the Canon extenders.

Share your experiences!

This is a bit of a niche topic, and there’s not a huge amount of information out there about it. If you’ve done this yourself, and gotten good OR bad results, I’d love it if you could share your experiences below in the comments. What kind of extenders did you stack together?  Did they need the extension tube in the middle to space them out like the Canon ones? Join the conversation below!

Photo of author

Dan Carr

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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63 thoughts on “How to Stack Canon Extenders”

  1. Hi
    It’s a nice article about stacking the Canon extenders with a 12mm tube, but it doesn’t say that infinit focus is not possible when you do that. This combo is pretty useless in situations outdoors. Please let me know if I am wrong, I would appreciate to stack my extenders.
    BR
    -Cyrill

    Reply
    • Hi Cyrill,

      You make a good point, and perhaps it’s one I need to expand on within the article as an update. Technically you do lose infinity focus, but in some cases super telephoto lenses actually focus past infinity, so this combination just brings thing back to around the infinity mark. It’s very hard to say what the result would be for every lens though, as each will be a bit different. In many wildlife photography situations with super telephoto lenses, losing the infinity focus isn’t a problem at all because the subject is well in front of that point. Whilst I can’t say exactly the result for your lens, what I can day is that it is most definitely not “useless in situations outdoors” as you have suggested. It can be most useable and indeed very useful.

      To ensure that I am not wrong, I just mounted a stacked 2x III and 1.4x III onto my 400mm f/4 DO II with a 12mm extension tube. I was able to focus easily on the house at the end of my street, which is some 150-200ft away from my office window. So for practical purposes, this simply isn’t an issue as any wildlife I would ever want to be photographing would be much closer than this and therefore I would have no issues focussing on it. You would really only run into a problem if, for some reason, you were trying to focus on something on the horizon. I don’t think this would be the typical usage for people stacking extenders. Most people are using it to get wildlife images.

      Reply
  2. Which is better: EF 2x II + EF 1.4x III or extender EF 2xIII + extension tube 12mm + EF 1.4x III? The 2xII is stackable without the tube, in front of the 1.4x.

    Reply
    • I didn’t know that the old II version of the 2x was stackable. However, the answer might depend on the lens you are using it with. The III extenders have slightly different electronics that helps AF performance with all Canon’s MKII super telephoto lenses, as well as the 200-400 f/4. If you don’t already own the II, it would make more sense to just use the IIIs with the tube IMO.

      Reply
  3. Hi, nice article. I use the 2x II and 1,4x (version one) in my old 300mm f/2,8 IS on a 7d mark II I have (slow) AF. They stack without the tubes. My question is: is it possible to stack two 2x converteres?

    Reply
    • You could stack two 2x, but the image quality would be significantly affected and you’d most likely have to focus manually. Also the viewfinder would be very dark. Theoretically it is possible though.

      Reply
  4. Great article! I have a 2xiii and 1.4xii and wanted to shoot the moon, will it focus that far? I haven’t found any info anywhere else.

    Reply
    • The difficult thing with that is that you need infinity focus which, as I mentioned, can be lost when using an extension tube. Some super telephoto lenses would still work, for the reasons I outlined in the article already. I do not think you would get it to focus on something like a 70-200 though. So it really depends what lens you are using… you’d have to try it and find out.

      Reply
        • You’re welcome, Sam! Glad you found it useful. Hope you subscribe in some form so that you get all the new posts 🙂

          Reply
    • I don’t think you would really need to have the sun filling the frame that much, but you could try. Just don’t burn your sensor!

      Reply
  5. I solved the infinity/focus problem by simply switching the externds. Put the 2x at first stage, then the 12mm tube, then the 1.4x. Works great, made a lot of solar eclipse pics with this combo. And I think the sun is at infinity…. 🙂 Of yourse you need a sun filter foil for solar pics!!

    Reply
    • Can you share your camera settings for the eclipse shots please? I most likely will shoot a 600mm f4L IS with a 2x extender(III)? Thanks in advance for the coaching, I intend going to Gatlin, TN(little longer eclipse than Nashville), but am uncertain as to optimal ISO setting.
      Regards, Chris.

      Reply
  6. Which of the two canon extender models MK III (2x and 1.4x) should connect directly to the camera body? Does the mounting order changes focusing, IQ or other parameters?

    Reply
  7. I have been using a canon 400mm 2.8 with a canon 2x lll and a Sigma 1401 1.4 extender they fit a little tight but it works I loose a little sharpness and the focus is slow on a 5d mk iv, in the metadata it does not show the 1.4. the sigma 1401 1.4 alone improves sharpness but I loose a little contrast.

    Reply
  8. I’m new to photography, using my wife’s Rebel t6S with EFS lenses. My understanding with the 2x III extenders is that the are incompatible with the EFS lenses due to interference of internal components. Do you think an extension tube, like the 12 mm, make use of the 2x possible with an EFS lense?

    Reply
    • I don’t think that would work because you can’t put an EF-S lens on an EF mount camera, and what you essentially have on the front of the extender is an EF mount. So regardless of the protruding glass element, there’s also the fact that the mounts are different. They have different locking pin placements.

      Reply
  9. I have akenco and ext 12mm does let me use efs mike Ontario ( I usually don’t because meds for double lung transplant makes me shake…macular degeneration makes auto focus a fantastic idea ) . Just found out can zoom to check focus in live view (T5i ). sept 2017 /lung transplant Oct 5 2016 wow !!!!!

    Reply
  10. MIKEONTARIO use magnifier + or – to zoom in live view . THE A7r will magnify in manual focus . Using sony 35x bridge and P900 (2000 mm ). Just an adenum to last comment .

    Reply
  11. I have 2 x ii and 2 x iii

    fits well together but you need to attach iii to body and ii on top of that obiviously becouse the new structure of the iii

    Reply
  12. I have an odly specific question maybe someone has the ability to test:
    I am purchasing a Canon 500mm f/4L Is USM lens (version 1), and was wondering if using a 1.4x (ii), a 12mm extension tube (Canon) and another 1.4x (ii) would retain the ability to autofocus? It would be f/8 but I have the 7D mk ii and know it can focus at Max f/8. I know the 2x looses autofocus so I was thinking this weird combo may retain autofocus. I can’t really go to a camera shop to ask they want have a Canon 1.4x ii or Canon 2x ii (most likely). Any comments?
    I will say extenders are common amoung us wildlife shooters because there are times when you need a 1200mm just because the subjects are that small or skiddish. The cheaper lenses like the 100-400mm (which I have as my on the go lens) just dont let in enough light if you throw a 2x on and now only have a Max of f/11.

    Reply
    • Something doesn’t seem quite right here… why would you not get AF when using the 2X extender on the 500mm f/4? That would give you an f/8 max, which should work fine on any camera that allows f/8 autofocus. I don’t think you need to use the convoluted double 1.4x method…

      Reply
  13. It seems like the article size I was aimed on never got changed after I stack 70-200 f2.8 together with 2x extender ii and 7D mark ii. Do you know why?

    Reply
  14. Thanks for this article. However, I am trying with a x2 III and a x1.4 III with a canon 12 mm ring in between. prime lens is EF2.8L 300mm canon.
    strangely so far not able to get focus in either manual our auto at about 1km away. i must be doing something wring, although set up looks like yours in above photo. ei camera body, then xx the 12mm then 1.4 then lens

    Reply
  15. Hi Dan,

    Can you confirm if you can focus with the stacked converters on your 400mm f4 DO II lens without having to use live view?

    I have the 1dx mk II and the 400mm F4 DO II lens with the 1.4 and 2x (series III converters) and a series I 12mm extension tube.

    My setup only allows me to autofocus in Live view mode. The camera does try to autofocus out of live view, but it just hunts for focus and doesn’t focus on anything.

    I’m wondering if Canon improved the camera to lens communication with the series II extension tube (like the one you used) which will allow this combo to autofocus without live view having to be engaged.

    The only way for me to test this is to buy the newer 12mm extension tube in order to test this combo and since no one locally stocks it these days, it would be wasted money if it still only focuses through live view mode.
    I can only assume that since you haven’t mentioned it once in this thread,that you can focus perfectly fine with this setup and that you don’t have to be in Live view mode for this setup to actually autofocus?

    Can you confirm?

    Thanks,
    Glenn.

    Reply
    • Hey Glenn, I can test this for you but I need to clarify… you say you are using the 1.4x and the 2x extenders. Do you mean you are using them stacked together simultaneously? Or are you just using one or the other, along with the extension tube?

      Reply
          • Yes Dan, I am aware of this fact that Canon cameras can only focus lenses down to f8.

            I clearly misunderstood when you said earlier in this thread that you took your camera outside and pointed it down your street and easily focused on the houses at the end of your street – I read this as you had pointed the camera down your street and used AF to focus, not that you manually focussed in order for this setup to work.

            I think you’ll be surprised to find that the 1dx mark ii will auto focus this setup when in Live view mode, as using the stacked converters tricks the camera into thinking it’s got a 560mm f5.6 lens on it and not a 1120mm f11.
            Try this for yourself with your camera to confirm for yourself that you can autofocus with this 1120mm setup.

            I was just hoping that if I upgraded to the series 2, 12mm extension tube that I would have been able to focus at 1120mm because again, the camera is tricked into thinking it has a 560mm f5.6 combo and again, I misunderstood your earlier comment when you said you easily focused down your street (my mistake).

            Additionally, Ken Rockwell confirms that when using both of the series II converters, he was still able to retain autofocus on his 5D mk III, I was hoping maybe the 1dx mk II could be tricked also, but I guess not.

            Quote Ken Rockwell:
            “Canon EF Extender 2x II and Canon EF Extender 1.4x II

            It works with both the Canon EF Extender 2x II and Canon EF Extender 1.4x II at the same time. Mount the TC-1.4x to the camera and the TC 2x to the lens and you have an 1,100mm f/11 lens!

            The EXIF data is in error. It still thinks this combo is an 800mm f/8. The good news is that because of this it will autofocus with the central AF area on my 5D Mark III!

            There is no real lens profile for this forbidden combination, and the combo produces a very little bit of green-magenta fringing.

            The great news is not only does it autofocus quickly (even if it may miss and fly right by the target), it is still ultrasharp at 1,100mm”.

            Reply
            • Yeah I can see where my wording might have caused some confusion. My apologies for not being clearer.

              “tricked into thinking it has a 560mm f5.6 combo and again” I think this is worth talking about. Yes, sometimes certain combinations of extenders and converters and extension tubes can “trick” the camera in this way. But to understand whether that is a positive thing you need to consider the reason for the f/8 limit in the first place.

              Accurate autofocus needs light, whether it is contrast detect of phase detect. Autofocus is performed with the aperture wide open, no matter what aperture you plan to take the shot at. This means that the max aperture is a determination of how much light you are able to send to the AF sensor or the camera sensor (contrast detection). The less light you send, the slower and less accurate autofocus is.

              If you trick them (there are other ways, too), Canon’s cameras are actually capable of focusing with smaller aperture than even f/11 if it’s a bright sunny day, but the results are slow and inaccurate. This f/8 “limit” is purely imposed by Canon because they feel that this is the point up to which you can get accurate and fast enough AF to be useful.

              So yes, you could use some method to trick the camera, but you’re not going to get enough light to be able to do a whole lot with it unless you are shooting high contrast static subjects.

              Reply
        • I use 5D mark iv, and want to stack 1.4 and 2 x with a 70-200 f2.8. I think technically it should still auto focus – but can only access a 25mm tube to test. It fails to focus at all if you do 1.4x then tube then 2x then lens, but will manually if you mount 2x then tube then 1.4x .
          Can you advise if the 25mm tube is causing the issue? Will the 12mm solve it and enable auto focus? ( this set up is for wildlife – birds – when having to travel lite and leave my 400 DO behind. )

          Reply
  16. Whoops, just for clarification, what I mean when I said this in the above post:

    “I was just hoping that if I upgraded to the series 2, 12mm extension tube that I would have been able to focus at 1120mm”.

    I meant to say, I was hoping with the series 2 teleconverter, I may be able to retain autofocus while looking through the viewfinder.

    Reply
  17. Hi, Great Article! Just thought I’d give my experience with stacking. I’ve recently upgraded to an EOS R and the awesome thing is that it auto focuses decently with a stacked 1.4x (II) and 2.0x (III) on an 70-200mm f2.8 IS. There is a 12mm extension in between the extenders. Order makes a massive difference though. With the 1.4x (II) first, the combo becomes a really low DoF macro lens that’s is really let’s me take really magnified insect and flower photos. But can’t manual focus on anything more than ~3m away. 2x (III) first and its good enough to take photos of sparrows in tall trees and on the roof of my house but infinity zoom is non-existent. I might try and get my hands on a 2.0x (II) at some stage so I can do away with the extension tube.

    Reply
  18. Very interested to know, when one stacks these two extenders, which one of the two is attatched to the camera body.
    many thanks

    Reply
  19. I use an old beat up, but with clean glass, 300 f/4L USM, non-IS. I love it. I get excellent results stacking 1.4× II and 2× II extenders, have been doing it for years. I always use a tripod, ball head, wired remote and, for videos, an LCD viewer. The viewer gives you a bright image in low light. Autofocus with stacked TCs and lenses now works with many new Canons. You can get a list online. Shooting dragonflies and butterflies as close as 6 or 7 feet I add an extension tube. Shooting cliff nesting birds, stacking is the way to go. I get shots that would otherwise cost me thousands of dollars. I did try third party (non-L) TCs in my old film days and was never happy with them.

    Reply
  20. Would it work to put an RF 2x converter on an R/RP/R6/R5 body, then a control ring adapter for EF, then a 1.4x iii EF converter, then an EF 100–400 f 4–5.6 ii lens? This should have no infinity focus issue. Has anyone tried this?

    Reply
  21. Can I combine a Kenko 2x and a Canon 1.4x without using an extension tube? It’s for astrophotography so I do not want to lose infinity focus with the extension tube. I already own the 1.4x and was thinking about getting the 2x.

    Reply
  22. Thanks for a great article

    I was trying hard to save up for the canon Mk11 100-400mm lens I already had the two extenders and a 70-200mm lens so I ordered the extension tube and tried it and it works a treat for what I want, no longer in a panic for the 100-400mm lens
    A really good article saved me a lot of pennies

    Reply
  23. note – the Canon 12mm II extension tube will NOT fit on the front end of the Canon 1.4X III converter. I wanted to do this so I could use the 1.4X with my 100mm 2.8L macro but the inside diameter of the extension tube is slightly too narrow for the protruding portion of the converter 🙁 The extension tube does fit on the front end of my old 2X II converter but I wanted to use the higher quality 1.4X III.

    Reply
    • My Canon 12mm II extension tube will fit perfectly well on the front end of my Canon 1.4X III converter. Maybe there are different versions?

      Reply
  24. Im trying to get some pics of wolves at a den but have to 1 mile 80ft away. The Sigma 150-600 C + Sigma TC-2001. It worked ok-ish as in you can tell there are wolves, but not can’t see any detail on the fur or anything. They take up a small portion of the frame, can a sigma tc-1401 + sigma tc-2001 be stacked, or what size extension tube would be needed?

    Reply
    • Honestly, it doesn’t matter what you do or stack together. At that distance you are never going to get clear, sharp photos. Stacking teleconverters barely works well when attached to a $15,000 prime lens. It is not going to get you anything with a cheaper zoom lens.

      You either need to get closer and use a remote camera or hide in a blind, or you need to pick a different subject I’m afraid.

      Reply
  25. Hi!!

    I would like to know if it’s posible to stack the canon 2x mark i extender with the mark ii or mark iii or if i would need an extension tube, or if it’s simply imposible.

    Thanks in advance

    Reply

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