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Old 27th of September 2013 (Fri)   #16
YashicaFX2
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Default Re: 70D's Dual Pixel AF and front/back focusing

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Really? My 7D can AF in that situation in LiveView. Not as fast, admittedly, as the 70D (I presume) but it'll do it.
OK. I got that idea from Canon's 70D promotional video. I guess I mis-interpreted it.

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The shorter answer is no.
In LV?
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Old 27th of September 2013 (Fri)   #17
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Default Re: 70D's Dual Pixel AF and front/back focusing

Has any 70D owners found it necessary to do any MFA?

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Old 27th of September 2013 (Fri)   #18
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Default Re: 70D's Dual Pixel AF and front/back focusing

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If you're an OVF user, then you won't benefit from the Dual Pixel AF technology. You do know that right?
Yes I am, and yes, I know. Live view is inappropriate for the action shooting I like most, so to me, the 70D's new AF method wouldn't make much of a difference.
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Old 27th of September 2013 (Fri)   #19
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Default Re: 70D's Dual Pixel AF and front/back focusing

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Has any 70D owners found it necessary to do any MFA?

Brian
I would think that MFA is still needed for traditional phase detect AF.
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Old 27th of September 2013 (Fri)   #20
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Default Re: 70D's Dual Pixel AF and front/back focusing

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Originally Posted by YashicaFX2 View Post
In LV?
OK, I am guessing that the PDAF in LiveView isn't iterative - purely because the whole - Is it in focus? - No - Move the lens - is it in focus now? - No - Move the lens a little bit - Is it in focus now? - routine would make AF very slow. And the whole point of having PDAF is LV is that it isn't supposed to be slow.
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Old 27th of September 2013 (Fri)   #21
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Default Re: 70D's Dual Pixel AF and front/back focusing

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I would think that MFA is still needed for traditional phase detect AF.
And also PDAF in LiveView - because I don't think it can compensate for lens errors, which is one of the main uses of MFA.
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Old 27th of September 2013 (Fri)   #22
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Default Re: 70D's Dual Pixel AF and front/back focusing

If you watch their sample video I'm guessing that the LV phase detect is interactive. At least it is able to sense moving objects and change focus.
http://www.youtube.com/watch?v=SovaYO5ucUI
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Old 27th of September 2013 (Fri)   #23
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Default Re: 70D's Dual Pixel AF and front/back focusing

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If you watch their sample video I'm guessing that the LV phase detect is interactive. At least it is able to sense moving objects and change focus.
http://www.youtube.com/watch?v=SovaYO5ucUI
What, like AI Servo, which isn't iterative.
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Old 27th of September 2013 (Fri)   #24
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Default Re: 70D's Dual Pixel AF and front/back focusing

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That's why different lenses require different MFA values.
Another issue is use of outside AF points - the Canon cameras tries to compensate for the field curvature of the different, known, Canon lenses which makes it harder for non-Canon lenses to do as well. Only continuous focus (closed loop) evaluations will make live-view able to perfectly cancel this effect whatever lens is used.

But it isn't unlikely that the 70D live view could manage better with outside AF points even if it is not using a closed loop. But in the end, open-loop AF really is very hard as most people should remember from the old "blue dot" debacle.
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Old 27th of September 2013 (Fri)   #25
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Default Re: 70D's Dual Pixel AF and front/back focusing

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And also PDAF in LiveView - because I don't think it can compensate for lens errors, which is one of the main uses of MFA.
I think you're right. I haven't come across any information that suggest MFA is possible in LV. I didn't think it would be an issue because I was under the impression that front/back focusing problems have been eliminated.

Last edited by lsquare : 27th of September 2013 (Fri) at 16:30.
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Old 27th of September 2013 (Fri)   #26
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Default Re: 70D's Dual Pixel AF and front/back focusing

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And it's this - the lens not moving accurately - that seems to be the major cause of front/back focusing. That's why different lenses require different MFA values. And, if the 70D's PDAF in LiveView, doesn't work iteratively then it can't help with this problem.

I call it 'Busted'.
I'm crossing my fingers and hope you're wrong! Hopefully DPR will take a hard look at the issue and address it once and for all.
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Old 27th of September 2013 (Fri)   #27
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Default Re: 70D's Dual Pixel AF and front/back focusing

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Originally Posted by hollis_f View Post
OK, I am guessing that the PDAF in LiveView isn't iterative - purely because the whole - Is it in focus? - No - Move the lens - is it in focus now? - No - Move the lens a little bit - Is it in focus now? - routine would make AF very slow. And the whole point of having PDAF is LV is that it isn't supposed to be slow.
Not necessarily. A traditional stop-and-go AF is very slow, because of the acceleration limitations of the lens, i.e. how many movements the lens can manage to perform per second.

But the 70D sensor supports partial read-outs, which should allow quite fast frame rates during AF - so it really should be possible for the camera to perform AF evaluations while the lens is busy performing a focus operation, allowing the camera to produce approximations of how muh further to move the focus. But no - I haven't spent the time to read up enough about the 70D to know if it does compute any focus while the lens is busy changing the focus. I don't even know if Canon have released such information. But partial sensor readouts can really give quite good focus times.
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Old 27th of September 2013 (Fri)   #28
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Default Re: 70D's Dual Pixel AF and front/back focusing

Wow a whole lot of guessing going on here for something that can be checked very easy
My 18-35 has a MFA of 0 at the 35mm end. I set the MFA to +20 and used quick focus and the image was way out of focus, but when I used LV pdaf it was perfect, the same as with the MFA at 0.
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Old 27th of September 2013 (Fri)   #29
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Default Re: 70D's Dual Pixel AF and front/back focusing

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Wow a whole lot of guessing going on here for something that can be checked very easy
My 18-35 has a MFA of 0 at the 35mm end. I set the MFA to +20 and used quick focus and the image was way out of focus, but when I used LV pdaf it was perfect, the same as with the MFA at 0.
Dual Pixel AF doesn't work with your Sigma lens.
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Old 27th of September 2013 (Fri)   #30
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Default Re: 70D's Dual Pixel AF and front/back focusing

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Dual Pixel AF doesn't work with your Sigma lens.
Site a source please. It sure seems to work fine for me
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Last edited by Varago : 27th of September 2013 (Fri) at 23:49.
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