This is a follow-up to Why does Canon and Nikon limit or disable autofocus beyond certain f-numbers? I'm doing this to separate the AF aperture requirements from the linked question above. My goal here is to create a canonical answer for Canon AF aperture limits, with complete information for every Canon EOS model since the EOS D30.
What apertures are required for Canon EOS DSLR cameras to autofocus? What apertures are needed to enable cross-type and/or high-precision autofocus?
To increase readability and avoid exceeding the answer length limit, this answer has been split across two posts. General information and APS-C cameras are covered in this post; full-frame and APS-H cameras are covered in a separate post below.
In general, Canon DSLRs require a maximum aperture of at least f/5.6 or wider to autofocus, although EOS-1 series cameras and certain newer models (including the EOS 5D Mark III, EOS 7D Mark II, and EOS 80D; essentially, any model with an AF sensor that has 45 or more points) are capable of focusing at f/8 with the center focus point. Depending on the camera model, and with some exceptions, a maximum aperture at least f/2.8 or f/4 or wider enables cross-type and/or high-precision focusing.
Where "autofocus does not function" is noted, phase-detection autofocus is normally impossible, either when shooting through the viewfinder or with the Quick AF mode in Live View, but it is generally possible to autofocus using the contrast detection-based Live AF and Face Detection Live AF modes in Live View.
In addition, when an extender (teleconverter) is being used and the resulting aperture is less than what is normally required for AF, it may be possible to enable AF by taping the three extender-specific pins (which are opposite of the raised pins) on the lens side of the extender to prevent it from communicating extender information with the lens and camera, so that the camera sees the lens's aperture as though no extender is attached. This is not guaranteed to succeed as the AF system is not designed to operate under these conditions, and the EXIF data will not reflect the use of the extender. Some third-party extenders may not communicate extender information with the lens and camera at all, with the same effect as the aforementioned "tape trick".
The limitations discussed hereafter generally do not apply to third-party zoom lenses that have maximum apertures of f/6.3 at the long end of the zoom range, as they actually report a maximum aperture of f/5.6 to the camera. Note, though, that faster third-party lenses should be able to autofocus as expected for their aperture, including any high-precision focusing capability normally supported by the lens and body.
All images in this answer should be attributed to Canon Inc unless otherwise noted.
All points function to f/5.6; the center point is normal-precision cross-type (it is both vertical- and horizontal-sensitive to f/5.6 and is not high precision at f/2.8). All other points are single-line (EOS D30 and D60: vertical sensitive only). Autofocus does not function below f/5.6.
Canon EOS D30/D60 AF array
Canon EOS 1000D AF array
The rectangles with longer sides horizontally oriented are vertical-sensitive.
The vertically oriented rectangles are horizontal-sensitive.
The square is sensitive both horizontally and vertically (cross-type).
Note that the EOS Rebel T3 (1100D) has essentially the same AF point layout as those in the next group of cameras, only that the center point is not high precision at f/2.8.
All points function to f/5.6. The center point is cross-type, and all other points are single-line. The center point is high-precision dual cross-type with f/2.8 or faster lenses. Autofocus does not function with lenses narrower than f/5.6.
Canon EOS Rebel T3i (600D) AF array
Canon EOS Rebel T1i and XSi AF point and position spacing
Source: Long-time Canon Technical Advisor Chuck Westfall
Note that the bold black and red rectangles with dots in the center are what actually appear in the viewfinder (all as black rectangles with dots in the center). The larger blue rectangles are the actual areas of coverage. Rectangles wider than tall are vertical-sensitive. Rectangles taller than wide are horizontal-sensitive.
All points function as cross type to f/5.6. The center point is high-precision dual cross-type with f/2.8 or faster lenses. Autofocus does not function with lenses narrower than f/5.6. With the following lenses, the center point is normal-precision single cross-type, as if they were f/5.6 lenses:
With the following lenses, the outside points of the AF array are single-line horizontal-sensitive, not cross-type:
(EOS Rebel T4i (650D): Though not included in the above link, this limitation is specified in the manual for this camera, page 99.)
Canon EOS 60D AF array
The same aperture limits for the EOS Rebel T4i (650D), 40D, 50D, and 60D apply to the 7D, only that the 7D has 19 AF points instead of 9.
EOS 70D: The above applies to focusing when using the viewfinder. In Live View, with Dual Pixel CMOS AF, phase-detection autofocus with apertures as small as f/11 is possible across about 65% of the total frame area (80% height by 80% width). Dual Pixel CMOS AF is fully supported with more than 100 EF lenses, including all EF lenses currently in production. Other lenses will autofocus in a hybrid phase-detection/contrast-detection mode when in Live View.
Rebel T6i and T6s: Sensor-plane phase detection AF is available but only in a hybrid mode.
Canon EOS 7D AF array
TODO: Expand with lens group information
45 points are available at all apertures f/5.6 or wider, 27 at f/8. With certain exceptions, the following apply:
Canon EOS 80D AF array
Source: Canon - Asia
With f/8 lenses, the blue points are horizontal-sensitive only. The red points remain cross-type. The nine points along the top and bottom are not sensitive with f/8 lenses or lens + extender combinations.
EOS 80D AF point sensitivity with f/8 lenses
Source: Canon - Asia
Canon EOS 7D Mark II AF array
Autofocus capabilities depend on which of the seven groups the lens in use falls into (see the EOS 7D Mark II manual):
Dual Pixel CMOS AF, as in the EOS 70D, is also available.
For general information and APS-C cameras, see the answer above.
All points function to f/5.6. The center point is cross-type, and all other points are single-line. The center point is high-precision cross-type with f/2.8 or faster lenses (but is not dual cross-type as it does not have diagonal-line sensors). Autofocus does not function with lenses with a maximum aperture narrower than f/5.6.
Note: the smaller black rectangles are what appear in the viewfinder. The larger blue and orange rectangles are the actual areas of coverage.
Canon EOS 6D AF array
All points function to f/5.6. The center point is cross-type, and all other points are single-line. The center point is high-precision cross-type with f/2.8 or faster lenses (but is not dual cross-type as it does not have diagonal-line sensors).
The invisible Assist AF points used in AI Servo AF function as horizontal-sensitive to f/5.6. With f/2.8 or faster lenses, two of these points function as cross-type.
Autofocus does not function narrower than f/5.6.
Canon EOS 5D Mark II AF array
The red "assist" points which are only active during AI Servo AF are not depicted in the viewfinder.
Source: Long time Canon Technical Advisor Chuck Westfall
Canon EOS 5D Mark II AF map with notations that show the actual areas of sensitivity superimposed over the smaller bold rectangles that actually appear in the viewfinder. Vertical blue rectangles are horizontally sensitive while horizontal blue rectangles are vertically sensitive.
Note that when using the EF 70-200mm f/2.8L USM lens (without IS) with an Extender, use the center point only as the other points may not focus correctly.
Canon EOS-1D Mark II AF array
Canon EOS-1D Mark III AF array
Canon EOS-1D Mark IV AF array
Canon EOS-1D X AF array
Autofocus capabilities depend on which of the eight groups the lens in use falls into (see the Canon EOS-1D X AF Setting Guidebook, pages 36-39, and Canon EOS 5D Mark III manual, pages 79-84, for more details; a complete and easier-to-navigate list of lenses can be found here):
Group E: Most f/5.6 lens and lens/extender combinations support 21 cross-type points in the center (none of the side points are cross-type, and there are no dual cross-type points). All 61 AF points and AF area selection modes are available. A few macro lenses are in this group as well:
EOS-1D X with firmware older than version 1.1.1 and EOS 5D Mark III with firmware older than version 1.2.1: Only the center point can be used (all other points are disabled) for the above EF 35-105mm lenses, and AF point expansion is not available. Autofocus does not function narrower than f/5.6.
TODO: Expand with lens group information
The arrangement of autofocus points is identical to that of the original EOS-1D X, but with several key enhancements. 61 points are available at all apertures f/8 or wider. For the purpose of determining autofocus capabilities, lenses will be divided into twelve groups from A through L. The following capabilities are available, subject to limitations as determined by the group in which a lens is placed:
Just wanted to point that the information about focus points in EOS 600D/550D/500D/450D might not be accurate.
" Canon EOS Digital Rebel XTi (400D), Rebel XSi (450D), Rebel T1i (500D), Rebel T2i (550D), Rebel T3i (600D), 30D
The center point is high-precision cross-type only when the aperture is at least f/2.8. If below f/2.8 but at least f/5.6, all points function as either horizontal or vertical sensitive only (not both). Below f/5.6, autofocus does not function. "
Canon website : "AF System/ Points 9 AF points (f/5.6 cross type at centre, extra sensitivity at f/2.8) "
Same is with 6D AF center point (f/5.6 cross type at centre, extra sensitivity at f/2.8), witch is same as in this article.
A recent discovery -- the Kenko teleconverters allow for autofocus at F/8 on most (if not all) Canon bodies. See for instance Art Morris: http://www.birdsasart-blog.com/2012/08/30/mega-amazing-discovery-800-f5-6-1-4x-tc-canon-eos-1dx/
I've started experimenting with the combination of a Kenko 2.0x teleconverter and a Canon 300 F/4 lens, which gives me a 600mm/F8. My initial experiments show that this combination on a 7D does, in fact, enable autofocus.
It should be noted that the combination needs good light; it doesn't seem to work well in poor light. It's slow. It's not always consistent. but it works.
It's too early for me to decide whether or not this is a combo I'd trust in field conditions on a regular basis (my initial take on the image quality is that they're sharp enough but I find the images a bit overexposed and the contrast is weak. Both are fixable either by adjustments on the camera or in post, but are definitely going to need to be evaluated further).
It does, however, work, and give me a 600mm lens for < $1400 if bought new. And it works well enough to at least be worth experimenting with. The Kenko 1.4x might be an interesting experiment on some of the F5.6 lenses as Morris notes, too.
I recently picked up a Yongnuo Extender 2X III, and tried it on my EF 400mm f/5.6L USM, and to my surprise the autofocus at f/11 actually works on both my 5D Mark IV and 5D Mark III bodies. I will point out I have not tried it in other than bright daylight; I expect it will fail as the light falls off, but normal daylight seems to allow these 2 bodies to continue to function. I did notice an odd thing on my Mark IV - I have to reduce my exposure by 2 stops compensation to get a balanced histogram, but the Mark III doesn't seem to have this issue. Further experimentation on my part might lead me to some reason for this. All in all, I was surprised by this result, and thinking it will help me as I sit in a field looking for those distant targets as long as they aren't moving too fast!
