The subject of autofocus (AF) at an f/8 maximum aperture is something that often comes up in my writings about cameras, lenses and telephoto lens techniques for subjects like sport and wildlife. It’s an often misunderstood subject in itself, but it also continuously raises questions about which cameras will still provide AF when used with a lens+extender combination that delivers a max aperture of f/8.

For now, I’m providing this information for Canon lenses because the majority of my lens and camera reviews in the past have been about Canon gear. In the future, I’ll also create a similar resource to tackle other relevant manufacturers such as Nikon.

A Two-Part Question

Whether a camera will autofocus with an f/8 max aperture actually doesn’t tell the whole story these days. Every year, Canon is expanding the capabilities of their AF systems and the result is that more and more cameras do feature AF at f/8, but to varying degrees. Some cameras will only allow the AF to work with a central AF point, and some will allow AF with the full gamut of AF points. The table below will tell you whether any sort of AF is possible with your camera at f/8, but it will also try to provide up-to-date notes on which AF points work. This last part has become a little more complex in recent years because there are now some newer lenses that deliver such improved AF performance, that they allow more AF points to be used at f/8 than some older lenses.

Is Your Lens f/8?

To find out the maximum aperture of your lens+extender combination, you first need to know the maximum aperture of the lens in its native form. This will be written on the lens, and in the specifications. The most common are f/2.8, f/4, f/5.6, f/6.3.

Next you need to know that that a 1.4x extender will increase the max aperture by 1-stop, and a 2x extender will increase the max aperture by 2-stops. For more information on extenders, and the math behind this increase, you can read my ultimate guide to extenders and teleconverters.

If you are a bit rusty on your f-stops, then you can refer to my f-stop chart in order to count either 1 or 2 stops up the chart from where your lens is.

Examples:

  • Canon 70-200 f/4 L IS + 2X Extender -> f/8
  • Canon 800mm f/5.6 L IS + 1.4X Extender -> f/8
  • Canon 500mm f/4 L IS II + 2X Extender -> f/8
  • Canon 100-400 f/4.5-5.6 L IS II + 1.4X Extender -> f/8

“Wait! My Camera Isn’t On the List!”

If you don’t see your camera listed in the table, such as an EOS Rebel camera, it does NOT deliver any kind of autofocus with an f/8 max aperture combination. Sorry 🙁

Special Note About the 5D Mark III

When this camera was first launched, it did not provide AF at f/8. This ability was added in a firmware update in April 2013, when the firmware was bumped up to V 1.2.1. If you have a 5D Mark III that does not appear to be working for AF at f/8, perhaps you have not got the firmware up to date. This is especially possible if you purchased a second-hand camera. Check that firmware number in the menu system!

Special Note About the 1D X

The 1D X also launched without the ability to AF at f/8, but this was quickly addressed with a firmware update in October 2012 to Version 1.1.1. If your 1D X doesn’t appear to be delivering AF at f/8, please check your firmware!

“Tricking” Cameras With 3rd Party Extenders

I’m aware that in some cases, it’s possible to trick some older cameras into providing some sort of basic AF with f/8 lens combinations. In particular, the 70D and 7D come up in conversation quite often when used with Kenko extenders, or by taping over the contacts of a Canon extender so the camera isn’t aware exactly what is attached to it. This sort of non-recommended functionality is pretty much impossible to comment on because there are too many permutations. The information contained in the table below, and the footnotes, are the official word from Canon. Whilst some other things may be possible with some fiddling and trickery, you are simply not going to get reliable AF in those situations, nor an AF speed that’s anything comparable to that which is officially supported. I simply wouldn’t bother with them, that’s my 2-cents. Cameras that do officially offer f/8 AF are available on the second-hand market for such great prices these days that it’s not worth faffing around with sub-standard options.

AF at f/8 Data Table

CameraAutofocus Possible at f/8 max?Which AF points are available?
1D X Mark IIYesUp to 61 points (with Version III extenders) See footnote.
1D XYesCentre cross-type AF point, or centre+ surround.
1D CYesCentre cross-type AF point, or centre+ surround.
1D Mark IVYesCentre AF point only (linear point)
1D Mark IIIYesCentre AF point only (linear point)
1D Mark IINYesCentre AF point only (linear point)
1D Mark IIYesCentre AF point only (linear point)
1DYesCentre AF point only (linear point)
1Ds Mark IIIYesCentre AF point only (linear point)
1Ds Mark IIYesCentre AF point only (linear point)
1DsYesCentre AF point only (linear point)
5DSYesCentre cross-type AF point, or centre+ surround.
5DS rYesCentre cross-type AF point, or centre+ surround.
5D Mark IVYesUp to 61 points (with Version III extenders) See footnote.
5D Mark IIIYesCentre cross-type AF point, or centre+ surround.
5D Mark IINoN/A
5D Mark INoN/A
6DNoN/A
6D Mark IIYesCentre AF point only, except for two lenses which can deliver 27 points. See footnote. (100-400 II and 200-400)
7DNoN/A
7D Mark IIYesCentre cross-type AF point, or centre+ surround.
80DYesCentre AF point only, except for two lenses which can deliver 27 points. See footnote.
70DNoN/A
60DNoN/A
50DNoN/A

Footnotes

6D Mark II

27 active points with the 6D Mark II and certain lenses (listed below). The ones highlighted in blue continue to work as cross-type AF points.

Unlike the original 6D, the Mark II will give you some use with f/8 combinations in the same was as the 80D.

  • AF at center AF point, when any Version I or II Canon tele extender is used with compatible EF tele lenses
  • AF at 27 focus points, and the central 9 points acting as cross-type points, with the following lens + extender combinations:
    • EF 100–400mm f/4.5–5.6L IS II lens, with Extender EF 1.4x III
    • EF 200–400mm f/4L IS Extender 1.4x lens, used with Extender EF 2x III

 

1D X Mark II & 5D Mark IV

61 AF Points

  • EF 100–400mm f/4.5–5.6L IS USM (lens versions I and II) + EF 1.4x III
  • EF 200–400mm f/4L IS USM with built-in 1.4x + EF 1.4x III
  • EF 200–400mm f/4L IS USM + EF 2x III
  • EF 400mm f/5.6L USM + EF 1.4x III
  • EF 400mm f/4 DO IS USM (lens versions I and II) + EF 2x III
  • EF 500mm f/4L IS USM (lens versions I and II) + EF 2x III
  • EF 500mm f/4.5L USM + EF 1.4x III
  • EF 600mm f/4L (all lens versions) + EF 2x III

13 AF Points

  • EF 300mm f/4L USM (IS and non-IS) + EF 2x III
  • EF 70–200mm f/4L USM (IS and non-IS) + EF 2x III

9 AF Points

  • EF 70-200mm f/4L USM (IS and non-IS versions) + EF 2x I and II
  • EF 100-400mm f/4.5-5.6L IS USM (lens versions I and II) + EF 1.4x I and II
  • EF 200-400mm f/4L IS USM (with built-in 1.4x) + EF 1.4x I and II
  • EF 200-400mm f/4L IS USM + EF 2x I and II
  • EF 300mm f/4L USM (IS and non-IS) + EF 2x I and II
  • EF 400mm f/5.6L USM + EF 1.4x I and II
  • EF 400mm f/4 DO IS USM (lens versions I and II) + EF 2x I and II
  • EF 500mm f/4L IS USM (lens versions I and II) + EF 2x I and II
  • EF 500mm f/4.5L USM + EF 1.4x I and II
  • EF 600mm f/4L USM (all lens versions) + EF 2x I and II
  • EF 800mm f/5.6L IS USM + EF 1.4x I, II and III
  • EF 1200mm f/5.6L USM + EF 1.4x I, II and III

 

EOS 80D

Lenses providing this broader 27-point coverage at f/8 effective maximum apertures with the EOS 80D are:

  • EF 100–400mm f/4.5–5.6L IS II + Extender EF 1.4x III
  • EF 200–400mm f/4L IS Extender 1.4x lens + Extender EF 2x III (built-in extender not used)

canon-80d-f8-autofocus

 

 

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