How can A6000 beat PDAF, doenst make sense?

Started 7 months ago | Questions
RonFrank
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PDAF like the A7.....
In reply to dpyy, 7 months ago

Once again we have a PDAF technology that is similar to the 5R/T/6/A7 that really does not solve the problem.  Will this technology work well in low light? No. Is this technology able to compete with a DSLR? No.

When a manufacture develops a technology that works better than the PDAF found in a DSLR we will know it because it  will not be disguised with words, rather they will trumpet it to the heavens and pronounce it a DSLR killer because that's what it will be.

Does PDAF work OK for the average consumer? Yes just not for action. Granted you can capture some action, but I think you are lucky to get a 50% in focus rate shooting with a 200mm lens.

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EinsteinsGhost
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Re: Remember the Aptina patents
In reply to captura, 7 months ago

captura wrote:

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.

Also a tiny sensor (relatively speaking) with much less data to move as well.

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123Mike
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Re: No mirror blackout
In reply to Bart Hickman, 7 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 SLTs have no mirror flap, and besides, the autofocusing on all camera happen before any mirror flap.

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Bart Hickman
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Re: No mirror blackout
In reply to 123Mike, 7 months ago

123Mike wrote:

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 SLTs have no mirror flap, and besides, the autofocusing on all camera happen before any mirror flap.

SLT's have the same advantage as mirrorless.

AF on DSLRs must stop working when the mirror begins going up.  This is why high-end DSLR's use predictive AF: the servo estimates where the focus should be set based on how fast the subject was moving at the time the mirror went up.

Mirrorless cameras don't need that because the AF sensors can keep making measurements right up until the picture is taken.  They need a little bit of predictive AF because there's some lag between when a focus measurement is taken and the motor responds, but this lag is small compared to the time it takes a mirror to flip up.

Bart

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dennis tennis
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Re: Metabones speedbooster for Canon EF
In reply to RonFrank, 7 months ago

I hope the new AF protocol can be used by Metabones to improve the AF.  That would be something.

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dpyy
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Re: PDAF like the A7.....
In reply to RonFrank, 7 months ago

RonFrank wrote:

Once again we have a PDAF technology that is similar to the 5R/T/6/A7 that really does not solve the problem. Will this technology work well in low light? No. Is this technology able to compete with a DSLR? No.

When a manufacture develops a technology that works better than the PDAF found in a DSLR we will know it because it will not be disguised with words, rather they will trumpet it to the heavens and pronounce it a DSLR killer because that's what it will be.

Does PDAF work OK for the average consumer? Yes just not for action. Granted you can capture some action, but I think you are lucky to get a 50% in focus rate shooting with a 200mm lens.

But as other posters in this thread has said, what IS the reason on sensor PDAF is slower than PDAF to begin with? Never understood that part. For example my NEX6 has on sensor PDAF but it doesn't improve the speed at all. It's just marketing crap.

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EinsteinsGhost
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Re: PDAF like the A7.....
In reply to dpyy, 7 months ago

RonFrank wrote:

Once again we have a PDAF technology that is similar to the 5R/T/6/A7 that really does not solve the problem. Will this technology work well in low light? No. Is this technology able to compete with a DSLR? No.

When a manufacture develops a technology that works better than the PDAF found in a DSLR we will know it because it will not be disguised with words, rather they will trumpet it to the heavens and pronounce it a DSLR killer because that's what it will be.

Does PDAF work OK for the average consumer? Yes just not for action. Granted you can capture some action, but I think you are lucky to get a 50% in focus rate shooting with a 200mm lens.

But as other posters in this thread has said, what IS the reason on sensor PDAF is slower than PDAF to begin with? Never understood that part. For example my NEX6 has on sensor PDAF but it doesn't improve the speed at all. It's just marketing crap.

Actually, PDAF does help NEX-6 although its effectiveness is more limited (and a first generation attempt). The a6000 design may be all new and more effective.

As for why mirror based PDAF has been more effective has to do with maturing of the technology since it was first put in Minolta a7000 back in 1985. It wasn't incredibly fast, IIRC with center spot only, but worked well. It also has to do with larger sensors (although only 70% of light was used, reflected off the mirror).

With digital sensors, one of the limiting factors has been the pixel size itself. It is likely that the new system is combining more of them to work together with very high rate, while receiving 100% of the light.

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stoppingdown
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Re: Metabones speedbooster for Canon EF
In reply to dennis tennis, 7 months ago

dennis tennis wrote:

I hope the new AF protocol can be used by Metabones to improve the AF. That would be something.

I was thinking the same, but first I'd like to understand how really faster is the A6000, beyond the marketing hype. It's relatively easy to autofocus with a short tele such as the 16-50; let's see how it does with the longest ones.

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Fabrizio Giudici
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stoppingdown
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Re: PDAF like the A7.....
In reply to EinsteinsGhost, 7 months ago

EinsteinsGhost wrote:

Actually, PDAF does help NEX-6 although its effectiveness is more limited (and a first generation attempt). The a6000 design may be all new and more effective.

As far as I know, PDAF on NEX-6 is only used to start the AF process, as PDAF tells the camera whether the lens should be focused farther or closer (contrast detection can't tell), thus avoiding some hunting. The NEX-6 completes the auto-focusing with contrast-detection. The A6000 might use PDAF more... in any case, I think we need to know more about this, and see some independent hands-on review.

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Fabrizio Giudici
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EinsteinsGhost
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Re: Metabones speedbooster for Canon EF
In reply to dennis tennis, 7 months ago

I hope the new AF protocol can be used by Metabones to improve the AF.  That would be something.

The lens AF mechanism will continue to be the limitation. Itay be possible to move the lens a bit faster in one direction (a criteria for PDAF) but these lenses are not optimized for fine tuning requirements with CDAF which is where the slow down is likely to be.

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EinsteinsGhost
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Re: PDAF like the A7.....
In reply to stoppingdown, 7 months ago

EinsteinsGhost wrote:

Actually, PDAF does help NEX-6 although its effectiveness is more limited (and a first generation attempt). The a6000 design may be all new and more effective.

As far as I know, PDAF on NEX-6 is only used to start the AF process, as PDAF tells the camera whether the lens should be focused farther or closer (contrast detection can't tell), thus avoiding some hunting. The NEX-6 completes the auto-focusing with contrast-detection. The A6000 might use PDAF more... in any case, I think we need to know more about this, and see some independent hands-on review.

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Fabrizio Giudici
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There are a couple of videos (one by Vogel and another by DanK) that show the a6000 at work and it looks impressive (not everything is shot under bright light conditions either) so it looks very promising. Of course, I would love to see more of such videos including other lenses (the FE 70-200G will be a superb candidate for it as one of its purposes is action photography).

As for the hybrid AF system, that is indeed the typical routine: PDAF to move the lens quickly near focus in one direction, and fine tuning with CDAF.

Speed will of course depend on read out rate, algorithm, the motor's capacity relative to the elements it must move and so on. Another key component to speeding up performance is to build more compact ciruitry (in fact, one of the goals that led to IC development). Yet another may be ability to have several pixels work together (this may be one of the more noticeable improvements and should also emhance performance in low light).

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stoppingdown
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Re: PDAF like the A7.....
In reply to EinsteinsGhost, 7 months ago

EinsteinsGhost wrote:

(the FE 70-200G will be a superb candidate for it as one of its purposes is action photography).

Indeed.

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tomtom50
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Re: Remember the Aptina patents
In reply to SHood, 7 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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More than that link is needed to tell the story. There a lot of on-sensor PDAF patents out there, and the system used on the Nikon 1 could be patented by any number of companies. Nikon, Aptina, a 3rd party under license, etc.

Aptina made the sensors, very possibly under license from someone else.

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hyenadog
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 7 months ago

correct me if i am wrong but in lower light (the NEX big AF weakness) phase detection is disabled and it has to rely on constrast detection .. if so if sony have made few imporvements in contrast detection then the NEX low light AF will still be uber crap compared to canikon dslr/oly CSC etc

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EinsteinsGhost
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to hyenadog, 7 months ago

correct me if i am wrong but in lower light (the NEX big AF weakness) phase detection is disabled and it has to rely on constrast detection .. if so if sony have made few imporvements in contrast detection then the NEX low light AF will still be uber crap compared to canikon dslr/oly CSC etc

At this point, you can't be correct or corrected since we don't have much to work with on the new system but only a handful of brief write ups and couple of videos (Vogel and DanK) that do show the possibilities in not so great light conditions.

I am pretty sure lower light performance was a consideration and should be better. The improvemebt is likely in how PDAF pixels work and how much closer they get to focusing for minimal CDAF fine tuning or if there is any need for that at all (after all, traditional PDAF has no fine tuning using CDAF).

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tomtom50
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to EinsteinsGhost, 7 months ago

EinsteinsGhost wrote:

correct me if i am wrong but in lower light (the NEX big AF weakness) phase detection is disabled and it has to rely on constrast detection .. if so if sony have made few imporvements in contrast detection then the NEX low light AF will still be uber crap compared to canikon dslr/oly CSC etc

At this point, you can't be correct or corrected since we don't have much to work with on the new system but only a handful of brief write ups and couple of videos (Vogel and DanK) that do show the possibilities in not so great light conditions.

I am pretty sure lower light performance was a consideration and should be better. The improvemebt is likely in how PDAF pixels work and how much closer they get to focusing for minimal CDAF fine tuning or if there is any need for that at all (after all, traditional PDAF has no fine tuning using CDAF).

Exactly. We do not know. The Nikon 1 system switches from PDAF to CDAF as light drops.

The Canon 70D system is full PDAF and works in low light

Earlier Sony systems were Hybrid AF (PDAF + CDAF) and the Sony press release uses that term as well.

http://www.dpreview.com/news/2014/02/12/sony-a6000-promises-worlds-fastest-af-and-11-fps-subject-tracking?utm_campaign=internal-link&utm_source=news-list&utm_medium=text&ref=title_0_12#press

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rinkos
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to dpyy, 7 months ago

newer sensor design and/or cpu is all the answer you will really need for this one .

its not a linear line and sometimes there are progressions in jumps . so for now this A6000 current solution is the fastest ..forget names and numbers regarding cameras ..just stick to the actual results on field ..thats my advice anyway

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EinsteinsGhost
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Re: How can A6000 beat PDAF, doenst make sense?
In reply to tomtom50, 7 months ago

tomtom50 wrote:

EinsteinsGhost wrote:

correct me if i am wrong but in lower light (the NEX big AF weakness) phase detection is disabled and it has to rely on constrast detection .. if so if sony have made few imporvements in contrast detection then the NEX low light AF will still be uber crap compared to canikon dslr/oly CSC etc

At this point, you can't be correct or corrected since we don't have much to work with on the new system but only a handful of brief write ups and couple of videos (Vogel and DanK) that do show the possibilities in not so great light conditions.

I am pretty sure lower light performance was a consideration and should be better. The improvemebt is likely in how PDAF pixels work and how much closer they get to focusing for minimal CDAF fine tuning or if there is any need for that at all (after all, traditional PDAF has no fine tuning using CDAF).

Exactly. We do not know. The Nikon 1 system switches from PDAF to CDAF as light drops.

Every camera suffers with lower light and/or smaller apertures. So this isn't a unique situation.

The Canon 70D system is full PDAF and works in low light

The Canon 70D "full PDAF" performance is nothing to write home about, even in good light. It is a significant improvement over DSLR Live View performance but it would make for a terrible "full PDAF" example for action stills.

Earlier Sony systems were Hybrid AF (PDAF + CDAF) and the Sony press release uses that term as well.

Well, the first was a PDAF+PDAF actually (a99). The 5R/6 were PDAF+CDAF. But, I'm unsure what your point is.

The a6000 may have been built on improvements to the older tech, or may be a completely new design with significant improvements. Time will tell but from what I have seen, it looks like a significant upgrade. The CIPA rating of 0.06s also points at very low shutter lag (not that NEX cameras since 5N have had it as an issue, they have been excellent at 0.022s in that regard).

About 20s into this video is a good demo

http://www.dpreview.com/news/2014/02/12/sony-a6000-promises-worlds-fastest-af-and-11-fps-subject-tracking?utm_campaign=internal-link&utm_source=news-list&utm_medium=text&ref=title_0_12#press

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nidri
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Re: Remember the Aptina patents
In reply to SHood, 7 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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That is some good detective work, Sir. Makes a whole lot of sense.

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symbology
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Re: Remember the Aptina patents
In reply to nidri, 7 months ago

I have not had a chance to go through this entire video yet, but what I have seen seems impressive.

http://www.youtube.com/watch?v=Q6N2KQ26fd4

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