- Messages
- 11,513
- Name
- Stewart
- Edit My Images
- Yes
So we had a customer ask us whether it was possible to achieve autofocus using the Canon EF 200-400mm f/1.4 L IS USM Extender 1.4x and an additional external 1.4x Extender on a Canon EOS-1D Mark III body.
At first glance you'd think it would be. Using both the internal and external extenders would make the lens 400-800mm f/8, and all the 1D-series bodies are rated to autofocus at f/8, so it ought to be straightforward.
But it's not so obvious. Apparently there's the potential for older bodies to get a bit confused when they're talking to a lens with a built-in extender and an external extender. This Canon USA blog post states quite clearly that Canon released a firmware update (v1.3.1) to clarify the communication between lens and camera and ensure that f/8 autofocus was possible. And the author of the blog ought to be authoritative if anyone is. But it's hard to get any other corroboration of this. And Canon released v1.3.2 of the firmware very quickly afterwards, so all the usual firmware download pages now state what's new in v1.3.2 and don't bother mentioning what was new in v1.3.1.
So, if in doubt, test it yourself. I borrowed a 1D Mk III from a friend, updated it to v1.3.2, mated it to an Extender 1.4x II and the 200-400mm lens, and the AF worked like a dream. Really, really fast. I didn't bother testing the Extender 1.4x III but that's obviously going to be at least as good.
The Canon USA blog post also stated that firmware updates had been released to fix this issue in the 1Ds Mark III and the 1D Mark IV. I haven't tested those bodies but I think it's reasonable to expect that's also correct.
I realise that this information is pretty esoteric. But if any TP members have this question in the future, here's the answer. And hopefully Google will pick up on it too, so that non-members with the same question will now be able to find the answer.
At first glance you'd think it would be. Using both the internal and external extenders would make the lens 400-800mm f/8, and all the 1D-series bodies are rated to autofocus at f/8, so it ought to be straightforward.
But it's not so obvious. Apparently there's the potential for older bodies to get a bit confused when they're talking to a lens with a built-in extender and an external extender. This Canon USA blog post states quite clearly that Canon released a firmware update (v1.3.1) to clarify the communication between lens and camera and ensure that f/8 autofocus was possible. And the author of the blog ought to be authoritative if anyone is. But it's hard to get any other corroboration of this. And Canon released v1.3.2 of the firmware very quickly afterwards, so all the usual firmware download pages now state what's new in v1.3.2 and don't bother mentioning what was new in v1.3.1.
So, if in doubt, test it yourself. I borrowed a 1D Mk III from a friend, updated it to v1.3.2, mated it to an Extender 1.4x II and the 200-400mm lens, and the AF worked like a dream. Really, really fast. I didn't bother testing the Extender 1.4x III but that's obviously going to be at least as good.
The Canon USA blog post also stated that firmware updates had been released to fix this issue in the 1Ds Mark III and the 1D Mark IV. I haven't tested those bodies but I think it's reasonable to expect that's also correct.
I realise that this information is pretty esoteric. But if any TP members have this question in the future, here's the answer. And hopefully Google will pick up on it too, so that non-members with the same question will now be able to find the answer.
