How can A6000 beat PDAF, doenst make sense?

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dpyy
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How can A6000 beat PDAF, doenst make sense?
10 months ago

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

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Sony a6000
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tomtom50
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

The a6000 doesn't beat PDAF. It is PDAF, on-sensor.

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SQLGuy
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

Why would it have to be slower? As long as the phase detect data can be read from the embedded pixels as quickly as they could be read from dedicated sensors, and as long as the autofocus processor is as fast, there's no inherent reason why OSPDAF shouldn't work as well as dedicated AF sensors.

Add to that the benefit of no possibility of back-focus/front-focus.

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parallaxproblem
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

It seems to come down to processing speed...  now the processors are (according to Sony) fast enough to perform the necessary calculations in realtime

Being based on-sensor there are potentially many benefits to this approach, not least that the distance being measured will be exactly the right one!  With a DSLR-type dedicated PDAF sensors in different location arrangement, any difference in light path between lens-to-sensor and lens-to-PDAF will be cause focus inaccuracies!

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Richard Ettinger
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

It has PDAF built onto the image sensor. they are dedicated to focusing.

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captura
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to tomtom50, 10 months ago

tomtom50 wrote:

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

The a6000 doesn't beat PDAF. It is PDAF, on-sensor.

It is essentially a system introduced by Sony with the NEX-5R, and employs both phase detection pixels on the sensor, and contrast detection to achieve fast autofocus; hence the term, 'hybrid.'

Here is a short description, from Steve's Digicams:

http://www.steves-digicams.com/news/sony_announces_new_nex-5r_with_hybrid_af_system_and_suite_of_playmemories_camera_and_mobile_apps.html

"This new model contains a host of new features, including a new Hybrid Autofocus System that uses 99 phase-detection AF points arrayed on the image sensor to detect a subject's distance and quickly lock focus on it, and then uses contrast-detection AF to confirm extremely fine, precise details.

The new Hybrid AF design allows users to track rapidly moving subjects via Phase Detect AF, as you would normally find in a dSLR model versus a Mirrorless Compact Camera. Sony is not the only one to integrate the Phase Detect AF Sensors into the main Imaging Sensor, so that no separate AF Sensor is needed to provide faster Focus. This is similar to the Hybrid AF technology we saw introduced in Nikon's 1 Series cameras, like the recently announced J2, which has 73 AF points on the main imaging sensor used for Phase Detect AF.

In Speed Priority Continuous Shooting Mode, the Sony NEX-5R switches to Phase Detect AF Tracking automatically using it's 99 AF points to maintain accurate focus on a subject while taking photos at up to 10 frames per second. That's the kind of performance you normally see from a high end Professional Grade dSLR, not from a smaller Compact Camera model like the NEX-5R. The evolution of technology we're seeing in newer cameras like this is amazing."

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GaryW
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

No flappy mirror thingie.  Less lag.

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Jim King
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to parallaxproblem, 10 months ago

Curious about the Bionz X image processaor. Is is unique to Sony or is it made by a third party, such as Fujitsu. The Fujitsu MB86S22AA is used by several camera makers (Nikon, Pentax) in their latest 24 MP bodies, I believe.

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Bart Hickman
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No mirror blackout
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

The dedicated sensor may well be able to determine a focus point quicker, but it has to cope with the mirror blackout.  If a subject is moving, the SLR must calculate where it thinks the subject will be when the picture gets taken perhaps 0.1s after the last AF measurement was made and then "catch up" once the mirror flips back up to try to reacquire the subject.  Predictive AF is usually only available on the higher-end DSLR's.

With the PDAF on the sensor, the camera can continue focusing with no interruptions.  No need (or much less need) for predictive AF.

It was only a matter of time before camera processors got fast enough to take advantage of the lack of mirror blackout.

Bart

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EinsteinsGhost
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to Jim King, 10 months ago

Curious about the Bionz X image processaor. Is is unique to Sony or is it made by a third party, such as Fujitsu. The Fujitsu MB86S22AA is used by several camera makers (Nikon, Pentax) in their latest 24 MP bodies, I believe.

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Bionz is a Sony product.

Nikon uses Expeed which is manufactured by Fujitsu. Not sure about Digic (which is used in Canon).

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DtEW
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

Simple.

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viking79
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

Even some dedicate CDAF cameras are faster than some PDAF cameras.  There is no hard rule saying PDAF is better than CDAF.

Historically, CDAF has been slower as it takes video from the sensor, does some image processing on it, and determines where it is sharper.  Better algorithms might take too much power or require more powerful processors to perform the calculations in real time (fast enough that the processor has some idle time).

Some huge limitations are how quickly you can read out data from the sensor, how quickly you can detect edges in that data, etc.  Now with faster sensors that can refresh the video at say 120 times or 240 times a second instead of 30 times a second, lens motors designed to step through a range of values very rapidly and precisely, software calibrated to the lens that can analyze the image to see how defocused a lens is, etc, and CDAF has become very fast.

CDAF has some weak points, like low light means it has to integrate the video longer to get strong enough edges to detect, etc.  So this quickly it can step through the focus range, etc.

Eric

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Riquez
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

Can anyone comment how the A6000 AF speed of 0.06 compares to the NEX6 speed  so we can get an idea of how much of an improvement it is?

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SHood
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Remember the Aptina patents
In reply to dpyy, 10 months ago

I think we are now seeing the benefits of the patent cross license agreement between Sony and Aptina last March.  Aptina developed the Nikon 1 sensor that has fast on-sensor PDAF.

http://www.imaging-resource.com/news/2013/03/01/aptina-sony-agree-to-cross-license-patent-portfolios

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captura
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Re: No mirror blackout
In reply to Bart Hickman, 10 months ago

Bart Hickman wrote:

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

The dedicated sensor may well be able to determine a focus point quicker, but it has to cope with the mirror blackout. If a subject is moving, the SLR must calculate where it thinks the subject will be when the picture gets taken perhaps 0.1s after the last AF measurement was made and then "catch up" once the mirror flips back up to try to reacquire the subject. Predictive AF is usually only available on the higher-end DSLR's.

With the PDAF on the sensor, the camera can continue focusing with no interruptions. No need (or much less need) for predictive AF.

It was only a matter of time before camera processors got fast enough to take advantage of the lack of mirror blackout.

Bart

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But in order to overcome these difficulties, Canon is trying new things with their DSLR, hence the dual pixel technology.

Canon develops new Dual Pixel CMOS AF technology for significantly improved autofocus performance during Live View shooting and when shooting movies

http://www.canon.com/news/2013/jul02e.html

Canon 70D with dual-pixel CMOS AF: The first DSLR that can autofocus videos

http://www.extremetech.com/electronics/160232-canon-70d-with-dual-pixel-cmos-af-the-first-dslr-that-can-autofocus-videos

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captura
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to viking79, 10 months ago

viking79 wrote:

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

Even some dedicate CDAF cameras are faster than some PDAF cameras. There is no hard rule saying PDAF is better than CDAF.

Historically, CDAF has been slower as it takes video from the sensor, does some image processing on it, and determines where it is sharper. Better algorithms might take too much power or require more powerful processors to perform the calculations in real time (fast enough that the processor has some idle time).

Some huge limitations are how quickly you can read out data from the sensor, how quickly you can detect edges in that data, etc. Now with faster sensors that can refresh the video at say 120 times or 240 times a second instead of 30 times a second, lens motors designed to step through a range of values very rapidly and precisely, software calibrated to the lens that can analyze the image to see how defocused a lens is, etc, and CDAF has become very fast.

CDAF has some weak points, like low light means it has to integrate the video longer to get strong enough edges to detect, etc. So this quickly it can step through the focus range, etc.

Eric

It's the physics. It's much easier to get very fast CDAF with a quarter-sensor camera like an M43 Olympus or Panasonic.

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captura
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Re: Remember the Aptina patents
In reply to SHood, 10 months ago

SHood wrote:

I think we are now seeing the benefits of the patent cross license agreement between Sony and Aptina last March. Aptina developed the Nikon 1 sensor that has fast on-sensor PDAF.

http://www.imaging-resource.com/news/2013/03/01/aptina-sony-agree-to-cross-license-patent-portfolios

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Yes, it could be. My 1" sensored Nikon 1 is definitely faster than my NEX-5R, and probably faster than the also-1" sensored RX100. But the Aptina sensor is only part of the story. The Nikon 1 has a very-smart dual core processor.

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paul1508
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Re: No mirror blackout
In reply to Bart Hickman, 10 months ago

Bart Hickman wrote:

dpyy wrote:

How can A6000 beat PDAF? Can someone explain the technology behind this? It doesn't matter how many points of autofocus they put on the sensor it should still be significantly slower than dedicated sensors?

The dedicated sensor may well be able to determine a focus point quicker, but it has to cope with the mirror blackout. If a subject is moving, the SLR must calculate where it thinks the subject will be when the picture gets taken perhaps 0.1s after the last AF measurement was made and then "catch up" once the mirror flips back up to try to reacquire the subject. Predictive AF is usually only available on the higher-end DSLR's.

With the PDAF on the sensor, the camera can continue focusing with no interruptions. No need (or much less need) for predictive AF.

It was only a matter of time before camera processors got fast enough to take advantage of the lack of mirror blackout.

Bart

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The next step would be to completely eliminate the mechanical shutter (electronic activation and deactivation of image capture) so PD-pixels don't have any blackout at all.

Can't wait to see this technology to come into mobile phones. In my opinion, the camera market below 300‚ā¨ is dead. You can get a NEX 3(whatever iteration is the newest one) for so cheap money and anything cheaper can't really stand out from 'good' smartphone-cameras.

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FuzzyQball
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 10 months ago

Just a different type of PDAF

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Bart Hickman
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Re: No mirror blackout
In reply to paul1508, 10 months ago

paul1508 wrote:

The next step would be to completely eliminate the mechanical shutter (electronic activation and deactivation of image capture) so PD-pixels don't have any blackout at all.

I think you'll always want to have the mechanical shutter be optional.  Electronic shutters don't completely shut off the sensor and the mechanical shutter keeps the sensor in the dark and therefore reduces noise.

Can't wait to see this technology to come into mobile phones. In my opinion, the camera market below 300€ is dead. You can get a NEX 3(whatever iteration is the newest one) for so cheap money and anything cheaper can't really stand out from 'good' smartphone-cameras.

Hopefully it scales to the small size.

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