Is AF-C basically a myth for NEX?

Started Feb 4, 2013 | Discussions
dpyy
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Is AF-C basically a myth for NEX?
Feb 4, 2013

I have a NEX6 camera and I've been missing a lot of moving shots for candid portraits in the street. Mostly because they are all out of focus. So I started training for this particular scenario. So first of all, I'm using a fast lens Z24 that allows me to go up to 1/200 or 1/300 with decent exposure.

Then secondly, I started using focus tracking. This way I can mark the person's face and then recompose. For the most part focus tracking is not the problem.

So finally the problem really is with AF-C. In burst mode, what I would expect is that the camera should constantly try to refocus after each shot, the box would turn green, makes the beep sound, and then take the shot. It kind of does this, but what ends up happening is that it would beep but the subject is still out of focus. So basically it lies...

The question is, anyone was able to use AF-C successfully for moving objects and burst mode? I'd imagine this is a very typical scenario. For example, the good old train-moving-towards you scenario where you would need to continuously change focus.

(P.S. I can take a video demonstrating this effect if I'm not explaining this clearly)

Sony Alpha NEX-6
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squirrelyfox
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 4, 2013

Anecdotally, yes I've noticed this and have been disappointed with the focus results of shooting multiple frames. I've always been meaning to test this out though in a more controlled manner to see how good/bad the AF in-between shots actually is (e.g. the train scenario or something similar). Anyone out there actually tried a more controlled test before to see how well this works?

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Brian Caslis
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 4, 2013

AF-C is a myth for any mirrorless camera except the Nikon 1 system and then only in good light. Contrast focus is just not the right mechanism for this. A number of people use AF-S on the Olympus OM-D since it focus very quickly and they just mash the shutter to take the shot right away. However, I think the focus on the NEX is just too slow to make this work.

In theory the NEX-6 might be able to handle tracking in good light. I have not used one myself for this and the reviews I've seen make we doubt it would be able to handle this.

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sean lancaster
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Re: Is AF-C basically a myth for NEX?
In reply to Brian Caslis, Feb 4, 2013

Brian Caslis wrote:

AF-C is a myth for any mirrorless camera except the Nikon 1 system and then only in good light. Contrast focus is just not the right mechanism for this. A number of people use AF-S on the Olympus OM-D since it focus very quickly and they just mash the shutter to take the shot right away. However, I think the focus on the NEX is just too slow to make this work.

In theory the NEX-6 might be able to handle tracking in good light. I have not used one myself for this and the reviews I've seen make we doubt it would be able to handle this.

At least Sony has figured it out. They had AF-C on the RX1 in an early production model and then removed the mode for the final model that shipped to consumers.

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Brian Caslis
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Re: Is AF-C basically a myth for NEX?
In reply to sean lancaster, Feb 4, 2013

sean lancaster wrote:

At least Sony has figured it out. They had AF-C on the RX1 in an early production model and then removed the mode for the final model that shipped to consumers.

True. I guess the main point I was trying to make was that no manufacturer currently has a good AF-C solution for mirrorless. This is one area where any DSLR will crush a mirrorless camera.

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dpyy
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Re: Is AF-C basically a myth for NEX?
In reply to Brian Caslis, Feb 4, 2013

Brian Caslis wrote:

sean lancaster wrote:

At least Sony has figured it out. They had AF-C on the RX1 in an early production model and then removed the mode for the final model that shipped to consumers.

True. I guess the main point I was trying to make was that no manufacturer currently has a good AF-C solution for mirrorless. This is one area where any DSLR will crush a mirrorless camera.

But the thing is, I have NEX6 with PDAF support. I was in good light. I had the lens that supported PDAF and verified that it was on.

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EinsteinsGhost
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 4, 2013

Brian Caslis wrote:

sean lancaster wrote:

At least Sony has figured it out. They had AF-C on the RX1 in an early production model and then removed the mode for the final model that shipped to consumers.

True. I guess the main point I was trying to make was that no manufacturer currently has a good AF-C solution for mirrorless. This is one area where any DSLR will crush a mirrorless camera.

But the thing is, I have NEX6 with PDAF support. I was in good light. I had the lens that supported PDAF and verified that it was on.

In NEX, On Sensor PDAF complements CDAF to improve CDAF performance, that I believe it succeeds in. However, for speedier approach, putting mirror on the NEX is the solution (LA-EA2 adapter) that makes AF all PDAF. Alternatively, you could try shooting with increased DoF, a reason why CDAF plus large sensor struggle for faster AF.

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viking79
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 4, 2013

dpyy wrote:

Brian Caslis wrote:

sean lancaster wrote:

At least Sony has figured it out. They had AF-C on the RX1 in an early production model and then removed the mode for the final model that shipped to consumers.

True. I guess the main point I was trying to make was that no manufacturer currently has a good AF-C solution for mirrorless. This is one area where any DSLR will crush a mirrorless camera.

But the thing is, I have NEX6 with PDAF support. I was in good light. I had the lens that supported PDAF and verified that it was on.

PDAF version 0.1.  Joking, but PDAF on sensor is new technology that hasn't been around too long.  Fuji used it on some point and shoots a few years back, and just in the last year or so we have Nikon V1, Sony NEX, Canon EOS-M, Samsung NX (300), and Fuji X100s which are all offering PDAF on sensor.

If you look at the early versions of autofocus in the 1980's, they were pretty bad too.  Early models were implemented in lens, then they went to phase detect, etc.  It took many generations for them to sort it out.

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DtEW
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Re: Is AF-C basically a myth for NEX?
In reply to viking79, Feb 4, 2013

viking79 wrote:

PDAF version 0.1. Joking, but PDAF on sensor is new technology that hasn't been around too long. Fuji used it on some point and shoots a few years back, and just in the last year or so we have Nikon V1, Sony NEX, Canon EOS-M, Samsung NX (300), and Fuji X100s which are all offering PDAF on sensor.

If you look at the early versions of autofocus in the 1980's, they were pretty bad too. Early models were implemented in lens, then they went to phase detect, etc. It took many generations for them to sort it out.

And this is precisely why I'm waiting for the next refinement.  Personal experience with Sony is that they are more avante garde with technologies (as they are very keen to slap a name on it and put it on the box even before the engineers are done with it), and the first/second revision after generally yields fairly substantial improvements.

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mswlogo
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Re: Is AF-C basically a myth for NEX?
In reply to DtEW, Feb 4, 2013

It has nothing to do with AF-C.

Note that on high frame rate (10 FPS) it does NOT Refocus and most SLR's "Frame Rate" is a rate stated WITH refocusing.

If you set it to the slower MultiShot mode the FPS WITH refocusing is about 1 FPS. Which is too slow for any kind of action shot.

If you use one of the adapters to a standard lens it will not use contrast focusing but I don't know how that impacts the refocusing frame rate.

It's a compromise for a compact size AF-C camera.

This is how Nex-7 is, I assume Nex-6 is the same in this regard.

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dpyy
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Re: Is AF-C basically a myth for NEX?
In reply to mswlogo, Feb 4, 2013

mswlogo wrote:

It has nothing to do with AF-C.

Note that on high frame rate (10 FPS) it does NOT Refocus and most SLR's "Frame Rate" is a rate stated WITH refocusing.

If you set it to the slower MultiShot mode the FPS WITH refocusing is about 1 FPS. Which is too slow for any kind of action shot.

If you use one of the adapters to a standard lens it will not use contrast focusing but I don't know how that impacts the refocusing frame rate.

It's a compromise for a compact size AF-C camera.

This is how Nex-7 is, I assume Nex-6 is the same in this regard.

Wow this is a HUGE caveat I wish more knew of this including myself. Does anyone know if EA2 solves this? I know it has faster AF but doesn't have AF in between multishot?

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Brian Caslis
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 4, 2013

I don't have this adaptor and none of the reviews I can find talk about continuous shooting. However I see no reason to expect any change from the normal NEX modes. The adaptor provides a different focusing mechanism, but there is no reason to expect faster continuous shooting. If it did, I'd expect more people would be buying these to get 10 fps capturing speeds which normally require top end DSLRs.

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CosmoZooo
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Re: Is AF-C basically a myth for NEX?
In reply to mswlogo, Feb 5, 2013

mswlogo wrote:

It has nothing to do with AF-C.

Note that on high frame rate (10 FPS) it does NOT Refocus and most SLR's "Frame Rate" is a rate stated WITH refocusing.

If you set it to the slower MultiShot mode the FPS WITH refocusing is about 1 FPS. Which is too slow for any kind of action shot.

If you use one of the adapters to a standard lens it will not use contrast focusing but I don't know how that impacts the refocusing frame rate.

It's a compromise for a compact size AF-C camera.

This is how Nex-7 is, I assume Nex-6 is the same in this regard.

Actually, you're quiet wrong here. All the specs I have seen from multiple review sites and reviews themselves have stated that NEX-6 has 10 fps with continuous focus. I've decided to let my post count and did some homework. The information below is from NEX-6 and 5R Handbook pdf which you can reference on Sony site:

This is for the regular Continuous Shooting mode which by the way is nothing ridiculous like 1fps. The normal burst mode is a DSLR competitive 3-3.5 fps:

Continuing to adjust the focus and exposure during continuous shooting

Set [Autofocus Mode] to [Continuous AF] (page 83).
Set [AEL w/ shutter] to [Off] (page 129).
• The exposure for the first image is set when you press the shutter button halfway down.
The camera continues to adjust the exposure for the remaining images.

And here is for the 10 fps:

Continuing to adjust the focus and exposure during
Speed Priority Continuous Shooting
Set [Autofocus Mode] to [Continuous AF] (page 83).
Set [AEL w/ shutter] to [Off] (page 129).
• If the Phase Detection AF does not work, the camera does not continue to adjust the focus
even if you set [Autofocus Mode] to [Continuous AF].
• The exposure for the first image is set when you press the shutter button halfway down.
The camera continues to adjust the exposure for the remaining images.

Now I am glad I did this because I did learn that one must have the AF-C enabled for focus to work in burst and also disable AEL with shutter. And of course there is the caveat for the focus in 10fps...must have PDAF, which means has to be bright enough and the aperture must be set below whetever that f.stop 6 something...but it is supposed to focus continuously in both modes.

And yes most entry and even mid-level DSLRs lock focus in their burst modes because to use phase detect they need the mirror down but it's pretty damn hard to move the mirror at a rate of 3fps don't you think, which is why mirrorless cameras can actually even attempt to do this.

EDIT:

SLT cameras that have translucent mirrors can actually burst faster with focus because the mirror is static.

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dpyy
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 5, 2013

dpyy wrote:

I have a NEX6 camera and I've been missing a lot of moving shots for candid portraits in the street. Mostly because they are all out of focus. So I started training for this particular scenario. So first of all, I'm using a fast lens Z24 that allows me to go up to 1/200 or 1/300 with decent exposure.

Then secondly, I started using focus tracking. This way I can mark the person's face and then recompose. For the most part focus tracking is not the problem.

So finally the problem really is with AF-C. In burst mode, what I would expect is that the camera should constantly try to refocus after each shot, the box would turn green, makes the beep sound, and then take the shot. It kind of does this, but what ends up happening is that it would beep but the subject is still out of focus. So basically it lies...

The question is, anyone was able to use AF-C successfully for moving objects and burst mode? I'd imagine this is a very typical scenario. For example, the good old train-moving-towards you scenario where you would need to continuously change focus.

(P.S. I can take a video demonstrating this effect if I'm not explaining this clearly)

Ok so I've actually went out and did the test, and the suggestions in this thread doesn't really help. Here's how I've setup the test:

  • I move towards and back with the center focused on a object while holding down shutter
  • Used a lens that support PDAF (Z24)
  • Used Aperture bigger than F/6
  • Autofocus mode in AF-C (Center)
  • AEL w/ shutter set to OFF (though I don't notice a difference either way)

So with that in mind, here are the tests. I've only uploaded one image per test because otherwise there would be too many photos.

==================================================

Test 1 - 1/250, F1.8

Video 1 - http://cl.ly/2d0j0k1S1f1L

==================================================

Test 2 - So maybe DoF is too shallow therefore I increased it to 3.2 (1/250, F3.2)

Video 2 - http://cl.ly/3G0k390G3r1b

==================================================

Test 3 - So maybe shutter is too slow so I tried (1/400, F3.2)

Video 3 - http://cl.ly/320J0m1s2z16

So the problem as you can see is that there are a lot of photos that are out of focus with the burst mode. So now the question is, how do I take photos of a moving object? I don't mean a speed bike or anything. Just a regular human being with candid shots? I wasn't even moving quickly forward and backward with the tiger but yet it fails so often!

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DtEW
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 5, 2013

The most constructive thing I'm going to say is:

Can you use an easier to focus-upon photo subject at a distance in which the shallow DoF (sometime exacerbated by being about a foot in front of the subject) isn't forced to choose between the tip of the snout, the hard edges of the eye(s), and the silhouette of the ears/body, much less the potted wheatgrass, and light in which you don't have to resort to ISO1600 and ISO3200?

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EinsteinsGhost
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Yes, it does.
In reply to Brian Caslis, Feb 5, 2013

Brian Caslis wrote:

I don't have this adaptor and none of the reviews I can find talk about continuous shooting. However I see no reason to expect any change from the normal NEX modes. The adaptor provides a different focusing mechanism, but there is no reason to expect faster continuous shooting. If it did, I'd expect more people would be buying these to get 10 fps capturing speeds which normally require top end DSLRs.

LA-EA2 turns NEX into an SLT. Anybody looking for shoot action with NEX, should consider EA2 for the purpose.

Now, on NEX-3, I'm limited by its rather slow 3 FPS or so. But AF is as fast as any comparable DSLR, if not better.

BTW, 10 FPS isn't common but NEX cameras that can achieve that, stand to benefit from EA2 and I believe NEX-6 is one.

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CosmoZooo
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But are you doing this in good light?
In reply to dpyy, Feb 5, 2013

So as others and I have said before PDAF doesn't work in low light. Now I don't really know how low is low and if someone does please comment but these shots are all high ISO 1600 and 3200 so this looks like a dim room lighting or something.

I have shot my kid on a swing on a playground in a bright day with certain level of success. I didn't lock the AEL but I think that's just to avoid locking exposure. So my advice is shoot in good light with low ISO high shutter and try it again.

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dpyy
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Re: Yes, it does.
In reply to EinsteinsGhost, Feb 5, 2013

EinsteinsGhost wrote:

Brian Caslis wrote:

I don't have this adaptor and none of the reviews I can find talk about continuous shooting. However I see no reason to expect any change from the normal NEX modes. The adaptor provides a different focusing mechanism, but there is no reason to expect faster continuous shooting. If it did, I'd expect more people would be buying these to get 10 fps capturing speeds which normally require top end DSLRs.

LA-EA2 turns NEX into an SLT. Anybody looking for shoot action with NEX, should consider EA2 for the purpose.

Now, on NEX-3, I'm limited by its rather slow 3 FPS or so. But AF is as fast as any comparable DSLR, if not better.

BTW, 10 FPS isn't common but NEX cameras that can achieve that, stand to benefit from EA2 and I believe NEX-6 is one.

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Thanks, that's such a great shot. In your opinion does EA2 increases the accuracy of focus in continuous mode? Is that how this is shot?

Have you seen the latest test I posted? Is that scenario something that you think EA2 would do better at?

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Pal2012
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Re: Is AF-C basically a myth for NEX?
In reply to dpyy, Feb 5, 2013

I can only share that AF-C works very really well with the LA-EA2 using PDAF that performs as well as the SLT cameras.

As far as low light, I had great performance shooting about 400 of these shot near Sundown with an overcast sky in early September:

Nex5+LA-EA2+Sigma 120-400mm handheld:























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jack scholl
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LA-EA2 . . . .
In reply to dpyy, Feb 5, 2013
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