How's the PD/CD Autofocus on NEX-6 compared to NEX-7?

Started Mar 8, 2013 | Discussions
K e n n e t h Senior Member • Posts: 1,065
How's the PD/CD Autofocus on NEX-6 compared to NEX-7?

I bought the NEX-7 as soon as it was released.

I love my NEX-7, but I could use faster, more accurate, and more reliable autofocusing.

For those who have the NEX-7 (Contrast Detect (sensor) Autofocus), and the NEX-6 (Contrast Detect (sensor) and Phase Detect Autofocus), how do the autofocusing of these two cameras compare?

With the same E-mount lens,

1.) Is the NEX-6 noticeable faster?

2.) More accurate?

3.) More reliable in autofocusing?

Feedback appreciated.

Sony Alpha NEX-6 Sony Alpha NEX-7
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blue_skies
blue_skies Forum Pro • Posts: 11,532
Re: How's the PD/CD Autofocus on NEX-6 compared to NEX-7?

kenneth_manila wrote:

I bought the NEX-7 as soon as it was released.

I love my NEX-7, but I could use faster, more accurate, and more reliable autofocusing.

For those who have the NEX-7 (Contrast Detect (sensor) Autofocus), and the NEX-6 (Contrast Detect (sensor) and Phase Detect Autofocus), how do the autofocusing of these two cameras compare?

With the same E-mount lens,

1.) Is the NEX-6 noticeable faster?

No.

In bright light, the CDAF is as-fast, if not faster, usually aided by prefocussing.

In low light, the recent FW updates have sped up all the CDAF based Nex-5N and Nex-7 cameras and lences.

PDAF will prevent hunting, but it can still take a moment to find focus.

Neither CDAF nor PDAF comes anywhere close to the LA-EA2 focusing time.

2.) More accurate?

It depends

For good subject contrast, the Nex-7 with CDAF is just as good as the Nex-6 with PDAF.  In fact, CDAF arguably is even more 'precise'.

But if a subject has soft outlines, or a background has harsh contrast, the CDAF will focus on the background contrast, whereas the PDAF will focus on the subject.

As 'snapshots', the PDAF based Nex-6 is easier, you can use multi-focus, face-detect, tracking, etc. all on, whereas on the CDAF based Nex-7 you would use center-focus lock + reframe to assure focus.

E.g. a typical 'snap' of two people in front of a building will have the people sharp with the Nex-6, and the building sharp with the Nex-7, using the same settings.

3.) More reliable in autofocusing?

Same as 2) ?

The center-focus lock + reframe is the most accurate method, but the center focus may not always find the right focus point, e.g. when DOF is very shallow, when you are doing macro shots, or when you have foreground (trees, flowers) against background (details).

I haven't tested much, but I expect, like the LA-EA2, the focus is satisfactory with PDAF up until a certain FL/F-stop combination. E.g. if you want to focus on the eye, the focus may be on the nose, or the ear (although I believe that the eye takes preference, if recognized).

For daytime shots, both CDAF and PDAF produce satisfactory results, but CDAF can have 'focus misses', and need photog's attention.

Or put it this way - handing the camera of to a novice with PDAF produces more keepers than the CDAF camera, even with instructions to 'center, hold, reframe'.

Feedback appreciated.

PDAF is better, and we will see it in the Nex-7, but it is not earth-shattering.

Also - moving subjects, especially oncomingsubjects (cars, people), require a larger DOF, or a proper photog's setup, they are not guaranteed to lock proper focus (use the LA-EA2 for that).

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Cheers,
Henry

 blue_skies's gear list:blue_skies's gear list
Sony Alpha NEX-6 Sony a6000 Sony a5100 Sony Alpha a7 II Sony Alpha a7R II +36 more
OP K e n n e t h Senior Member • Posts: 1,065
Thanks, Henry

blue_skies wrote:

In bright light, the CDAF is as-fast, if not faster, usually aided by prefocussing.

In low light, the recent FW updates have sped up all the CDAF based Nex-5N and Nex-7 cameras and lences.

PDAF will prevent hunting, but it can still take a moment to find focus.

Neither CDAF nor PDAF comes anywhere close to the LA-EA2 focusing time.

I was hoping the hybrid autofocusing will make the NEX-7n much faster.

My NEX-7 autofocus is too slow and inaccurate, especially indoors.

2.) More accurate?

It depends

For good subject contrast, the Nex-7 with CDAF is just as good as the Nex-6 with PDAF. In fact, CDAF arguably is even more 'precise'.

But if a subject has soft outlines, or a background has harsh contrast, the CDAF will focus on the background contrast, whereas the PDAF will focus on the subject.

As 'snapshots', the PDAF based Nex-6 is easier, you can use multi-focus, face-detect, tracking, etc. all on, whereas on the CDAF based Nex-7 you would use center-focus lock + reframe to assure focus.

E.g. a typical 'snap' of two people in front of a building will have the people sharp with the Nex-6, and the building sharp with the Nex-7, using the same settings.

Wow.  Sounds like the NEX-7n will not be much better in this department, compared to my NEX-7.

The center-focus lock + reframe is the most accurate method, but the center focus may not always find the right focus point, e.g. when DOF is very shallow, when you are doing macro shots, or when you have foreground (trees, flowers) against background (details).

I haven't tested much, but I expect, like the LA-EA2, the focus is satisfactory with PDAF up until a certain FL/F-stop combination. E.g. if you want to focus on the eye, the focus may be on the nose, or the ear (although I believe that the eye takes preference, if recognized).

For daytime shots, both CDAF and PDAF produce satisfactory results, but CDAF can have 'focus misses', and need photog's attention.

Or put it this way - handing the camera of to a novice with PDAF produces more keepers than the CDAF camera, even with instructions to 'center, hold, reframe'.

PDAF is better, and we will see it in the Nex-7, but it is not earth-shattering.

Also - moving subjects, especially oncomingsubjects (cars, people), require a larger DOF, or a proper photog's setup, they are not guaranteed to lock proper focus (use the LA-EA2 for that).

I was really hoping for improved autofocus performance, with this hybrid technology.

I planned to get the LA-EA2 and the SAL1650, but I was spoiled by the SEL18200--it is so convenient to only use one lens.

Thanks for sharing your observations, Henry.

Jeff Kott Senior Member • Posts: 1,164
Re: How's the PD/CD Autofocus on NEX-6 compared to NEX-7?

blue_skies wrote:

As 'snapshots', the PDAF based Nex-6 is easier, you can use multi-focus, face-detect, tracking, etc. all on, whereas on the CDAF based Nex-7 you would use center-focus lock + reframe to assure focus.

I'm not sure I understand what you're saying here. I recently bought the 35/1.8 as my first autofocus lens for my Nex 7 for taking snapshots (mostly of my young daughter). I almost only use face detect AF and it's working great.

Why are you saying you wouldn't use face detect AF with the Nex 7?

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Jeff Kott

blue_skies
blue_skies Forum Pro • Posts: 11,532
Re: How's the PD/CD Autofocus on NEX-6 compared to NEX-7?
 

Jeff Kott wrote:

blue_skies wrote:

As 'snapshots', the PDAF based Nex-6 is easier, you can use multi-focus, face-detect, tracking, etc. all on, whereas on the CDAF based Nex-7 you would use center-focus lock + reframe to assure focus.

I'm not sure I understand what you're saying here. I recently bought the 35/1.8 as my first autofocus lens for my Nex 7 for taking snapshots (mostly of my young daughter). I almost only use face detect AF and it's working great.

Why are you saying you wouldn't use face detect AF with the Nex 7?

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Jeff Kott

Only if the faces are well lit against a darker background. But better to avoid a lamp or a tv in the background.

A 'bright' background under low light conditions, especially with a playmate, is not always going to work. Face recognition may fail, and the background will win focus.

A single subject, in the center, will usually get proper focus, but when off-center it depends on the lighting conditions.

I have examples of (almost back to back) shots with the Nex-7 which show failures and successes. (well lit) heads and torsos trigger proper focus, dark or non-contrasty heads/torsos and full body shots miss focus (bright background).

The Nex-6 is more reliable in this sense. I use center focus on the CDAF based Nexes.

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Cheers,
Henry

 blue_skies's gear list:blue_skies's gear list
Sony Alpha NEX-6 Sony a6000 Sony a5100 Sony Alpha a7 II Sony Alpha a7R II +36 more
Jeff Kott Senior Member • Posts: 1,164
Re: How's the PD/CD Autofocus on NEX-6 compared to NEX-7?

But you know when face detect AF is working because the EVF or rear LCD image shows a box around the head that is focused on, so why would you get misfocused images? If you don't see the box where you want it, don't push the shutter button.

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Jeff Kott

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