AF at f8/f11 with the 70D

[Azathoth]

The 70D doesn't focus with the normal phase detection with a f8 lens, right?

But what about the dual pixel liveview AF?

Does it focus at f8 or f11?

If i buy for example a EF 100-400 mm f4.5-5.6 (the old one) and stick a 2x extender i get a 200–800 mm f/9–11. Does it focus using liveview AF?

[TTMartin]

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@Azathoth wrote:

The 70D doesn't focus with the normal phase detection with a f8 lens, right?

But what about the dual pixel liveview AF?

Does it focus at f8 or f11?

If i buy for example a EF 100-400 mm f4.5-5.6 (the old one) and stick a 2x extender i get a 200–800 mm f/9–11. Does it focus using liveview AF?

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Yes, It will AF, but,  towards the center of the frame only.

[Waddizzle]

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@Azathoth wrote:

The 70D doesn't focus with the normal phase detection with a f8 lens, right?

But what about the dual pixel liveview AF?

Does it focus at f8 or f11?

If i buy for example a EF 100-400 mm f4.5-5.6 (the old one) and stick a 2x extender i get a 200–800 mm f/9–11. Does it focus using liveview AF?

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I would not expect it to autofocus.  The center focus point is the most sensitive, and only certain Canon camera models can focus with the center point at f/8, and no higher. 

I do not think the 70D is one of those cameras that have a center point that can focus at f/8.

[Azathoth]

TTmartin: Even at f11 with the 2x extender?

[Azathoth]

I know it won't focus using the viewfinder. But will AF using Dual Pixel Flexi zone mode?

Here in this link:
http://www.imaging-resource.com/news/2014/02/27/canon-dual-pixel-cmos-af-autofocus-secrets-of-the-ca...

It says: "At the other end of the scale, Dual Pixel CMOS AF supports autofocusing with maximum apertures as small as f/11, a full two stops smaller than is possible with the 70D's TTL-SIR-AF system."

and:

"When it comes to video focusing, though, even Full HD (1,920 x 1,080 pixel) resolution is so much lower than the 70D's 20-megapixel still image resolution that the slightly lower PDAF accuracy of the Dual Pixel CMOS AF system matters not a bit, while its ability to focus smoothly and continuously at apertures down to f/11 is a huge benefit."

These are quotes by Chuck Westfall  himself, but did anyone really tried this?

[Waddizzle]

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@Azathoth wrote:

I know it won't focus using the viewfinder. But will AF using Dual Pixel Flexi zone mode?

Here in this link:
http://www.imaging-resource.com/news/2014/02/27/canon-dual-pixel-cmos-af-autofocus-secrets-of-the-ca...

It says: "At the other end of the scale, Dual Pixel CMOS AF supports autofocusing with maximum apertures as small as f/11, a full two stops smaller than is possible with the 70D's TTL-SIR-AF system."

and:

"When it comes to video focusing, though, even Full HD (1,920 x 1,080 pixel) resolution is so much lower than the 70D's 20-megapixel still image resolution that the slightly lower PDAF accuracy of the Dual Pixel CMOS AF system matters not a bit, while its ability to focus smoothly and continuously at apertures down to f/11 is a huge benefit."

These are quotes by Chuck Westfall  himself, but did anyone really tried this?

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The linked article describes two focusing systems, [and it is not clear when and why two image sensing systems are used in the 70D.]  The Dual Pixel AF system is used with the [camera's main] image sensor itself, during video and Live View shooting, when the mirror is raised.   [The TTL-SIR AF system is used when shooting through the viewfinder, when the mirror is not raised.]

http://www.imaging-resource.com/PRODS/canon-70d/canon-70dDUAL_PIXEL_AF.HTM

"With the advent of full-sensor phase-detect AF in the Canon 70D, the same is now true for it as well: When the system says things are in focus, there's no question of whether a separate AF sensor is lined up properly with the image sensor; they're one and the same. (Of course, this is only true for Live View mode. In standard shooting, the 70D still uses a separate phase-detect sensor that's subject to the same tolerances as any other DSLR. And even with the on-chip phase-detect, there are always possibilities for error with any system. In our testing, we found the 70D's focusing to be very accurate.)"

[Waddizzle]

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@Azathoth wrote:

TTmartin: Even at f11 with the 2x extender?

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The f/8 limitation is imposed through firmware.  It is not a hardware limitation, per se. 

Even still, the firmware allows for numerous exceptions to the "f/8 rule" [with many "L" lenses], and the EF 100-400mm f/4.5-5.6L is a perfect example of this type of allowance. 

Despite the 100-400mm lens having its' performance bumped up to f/9-11 with the EF 2X III extender, the lens will still focus properly with certain Canon cameras.  [The lens is listed to be used with the extender.]  The compatible camers would include the 1D Series and the 7D Mark II, and should include any other Canon DSLR cameras that have a center AF point that focus at f/8.

[TTMartin]

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@Azathoth wrote:

TTmartin: Even at f11 with the 2x extender?

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In towards the middle of the image in LiveView, Yes.

[Azathoth]

Ok, thanks TTMartin.

[TTMartin · Accepted solution]

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@Azathoth wrote:
Ok, thanks TTMartin.

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Just don't expect to AF on birds in flight, fast moving sports, or low contrast situations, but, a bird on branch with good contrast sure.