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Author Topic: Canon Dual Pixel Liveview Autofocus  (Read 26576 times)

neuroanatomist

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #30 on: July 02, 2013, 10:47:18 AM »
I'm also hoping that the pixels aren't all split in a left/right horizontal pattern, as the video shows, but that half of them are split vertically, because no one would want the AF system to be sensitive to horizontal contrast only.

Based on what I've read, including a statement from Chuck Westfall who was asked for clarification on the matter, they are all split in the same direction.  That means the Dual Pixel CMOS phase AF system is a giant vertical line sensor, responsive only to horizontally-oriented details.
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Re: Canon Dual Pixel Liveview Autofocus
« Reply #30 on: July 02, 2013, 10:47:18 AM »

traveller

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #31 on: July 02, 2013, 11:05:13 AM »
I'm also hoping that the pixels aren't all split in a left/right horizontal pattern, as the video shows, but that half of them are split vertically, because no one would want the AF system to be sensitive to horizontal contrast only.

Based on what I've read, including a statement from Chuck Westfall who was asked for clarification on the matter, they are all split in the same direction.  That means the Dual Pixel CMOS phase AF system is a giant vertical line sensor, responsive only to horizontally-oriented details.

This will be the 80D's big selling point - "Cross-type Dual Pixel CMOS"  ;D

Random Orbits

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #32 on: July 02, 2013, 11:12:51 AM »
I'm also hoping that the pixels aren't all split in a left/right horizontal pattern, as the video shows, but that half of them are split vertically, because no one would want the AF system to be sensitive to horizontal contrast only.

Based on what I've read, including a statement from Chuck Westfall who was asked for clarification on the matter, they are all split in the same direction.  That means the Dual Pixel CMOS phase AF system is a giant vertical line sensor, responsive only to horizontally-oriented details.

Any guess as to whether the next generation will have a quad split (2x2) to do both vertical and horizontal or would it be better to use the next neighboring pixel of of the same color instead?

tron

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #33 on: July 02, 2013, 11:18:57 AM »
If they like "playing" with the sensors they might as well make a lower noise/higher DR one  ::)  ;D  8)
(Let the debates begin... )

tron

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #34 on: July 02, 2013, 11:34:54 AM »
Or to put it another way, the noise characteristics of the 70D should be about that for a 40MP APS-C sensor using the same sensor technology without the PDAF split.
But then the two parts are combined to one pixel so it isn't it a kind of pixel binning?

BruinBear

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #35 on: July 02, 2013, 12:20:51 PM »
According the Canon the EOS 70D's Dual Pixel CMOS AF system has the following key characteristics:

Usable phase detection AF area covers 80% of the frame horizontally and vertically
AF works at apertures down to F11
AF works in light levels as low as 0 EV
Can work with face detection to keep moving subjects in focus

 :o
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alan_k

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #36 on: July 02, 2013, 12:21:49 PM »
This is from the DP-Review hands-on Preview (bold mine)

Quote
According the Canon the EOS 70D's Dual Pixel CMOS AF system has the following key characteristics:

    Usable phase detection AF area covers 80% of the frame horizontally and vertically
    AF works at apertures down to F11
    AF works in light levels as low as 0 EV
    Can work with face detection to keep moving subjects in focus

Does this mean, for example, I could get AF on a 70-300L + 2xTC, and if so, only in live-view?

e: you read my mind!!!  :o
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Re: Canon Dual Pixel Liveview Autofocus
« Reply #36 on: July 02, 2013, 12:21:49 PM »

neuroanatomist

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #37 on: July 02, 2013, 12:24:54 PM »
This is from the DP-Review hands-on Preview (bold mine)

Quote
According the Canon the EOS 70D's Dual Pixel CMOS AF system has the following key characteristics:

    Usable phase detection AF area covers 80% of the frame horizontally and vertically
    AF works at apertures down to F11
    AF works in light levels as low as 0 EV
    Can work with face detection to keep moving subjects in focus

Does this mean, for example, I could get AF on a 70-300L + 2xTC, and if so, only in live-view?

e: you read my mind!!!  :o

Sure...but you could do that with Live View on any camera (although not with phase detect AF).
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Mt Spokane Photography

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #38 on: July 02, 2013, 12:33:38 PM »
I'm also hoping that the pixels aren't all split in a left/right horizontal pattern, as the video shows, but that half of them are split vertically, because no one would want the AF system to be sensitive to horizontal contrast only.

Based on what I've read, including a statement from Chuck Westfall who was asked for clarification on the matter, they are all split in the same direction.  That means the Dual Pixel CMOS phase AF system is a giant vertical line sensor, responsive only to horizontally-oriented details.

That's also what I surmised from Canon's video.  However, I believe that in Portrait mode, the sensor would be only seeing vertical details unless the camera is able to switch between the two automatically, which doesn't seem likely - at least not in a mid range model.
 
I am wondering about things like banding, or a new type of artifact that might appear due to the divided photo sensors.  That's pretty dependent on the actual fine details of how it works, something that we are not going to get from Canon.
 
As to patents, the sensor sounds like it uses this recent patent from Canon.
 
http://translate.google.com/translate?twu=1?sl=auto&tl=en&u=http%3A//egami.blog.so-net.ne.jp/2012-08-12
 
After reading the patent document, I found it to be very complex, but it is almost certainly what we are seeing.
 
The wording is very engineering like, and looks like something intended for a mirrorless camera, which is why it was not anticipated to appear in a DSLR first.
 
While AF is said to be 30% faster, its obviously not yet going to beat conventional phase detect AF for speed.  However, with more computing horsepower as might happen with a dual Digic 5+ processor or a newer version of Digic, we might see the mirror go away for good.
« Last Edit: July 02, 2013, 12:48:22 PM by Mt Spokane Photography »

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #39 on: July 02, 2013, 12:58:26 PM »
Here is another video showing what the focus pulls look like when you use the touchscreen to focus while you are shooting in live view.  It actually looks pretty nice.  They also have some examples of auto focus ect.  if you watch after the credits in the middle of the video they replay the video with an overlay showing focus info and some metadata.

https://www.youtube.com/watch?v=Tf0BBNr6Epk&feature=player_embedded

funkboy

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #40 on: July 02, 2013, 07:50:56 PM »
Does it have AFMA?

check the dprevew preview.

The 70D does have AFMA for the traditional 19 point AF sensor (unlike the 60D), but the dual pixel system doesn't need AFMA because the AF sensor & the image sensor are one in the same.
« Last Edit: July 02, 2013, 07:53:20 PM by funkboy »

funkboy

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #41 on: July 02, 2013, 08:05:30 PM »
If this thing is already doing pixel-binning for 40 half-pixels, wouldn't it be trivial to have it pixel-bin 4x and make a very nice noise-free 10MP image?  I'm sure that Digic5+ can handle that...

In the telecom world anyway, having 4 signals to work with and compare makes a huge difference in the quality of the transmission.

Mt Spokane Photography

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #42 on: July 02, 2013, 09:14:59 PM »
Does it have AFMA?

check the dprevew preview.

The 70D does have AFMA for the traditional 19 point AF sensor (unlike the 60D), but the dual pixel system doesn't need AFMA because the AF sensor & the image sensor are one in the same.

AFMA is certainly not well advertised, it wasn't in the specification, but is welcome.
 
Hopefully the new dual pixel AF is accurate, contrast detect in the 5D MK III has been shown to be inaccurate.  I think we will have to wait and see, the tolerances of a in photosite  phase detect system would need to be almost impossibly accurate, so there is likely some sort of calibration, and that implies mis-calibration is possible.
I'm sure we will find out.

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #42 on: July 02, 2013, 09:14:59 PM »

neuroanatomist

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #43 on: July 02, 2013, 09:39:59 PM »
AFMA is certainly not well advertised, it wasn't in the specification, but is welcome.

Canon USA doesn't list AFMA in the specs of any camera with the feature.   Canon UK does, though.
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verysimplejason

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #44 on: July 03, 2013, 04:06:59 AM »
I hope 6D mark II would have 3D sensor + 70D features.  :)

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Re: Canon Dual Pixel Liveview Autofocus
« Reply #44 on: July 03, 2013, 04:06:59 AM »