FAQ FAQ  Forum Search   Events   Register Register  Login Login

AF-C, AF-S, & Fast Hybrid

Author
Miranda F View Drop Down
Senior Member
Senior Member

Joined: 11 January 2014
Country: United Kingdom
Location: Bristol
Status: Offline
Posts: 3847
Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Topic: AF-C, AF-S, & Fast Hybrid
    Posted: 19 March 2021 at 20:01
I am becoming increasingly puzzled by the AF behaviour of my E-mount cameras and lenses (A7Rii and Nex-6). I have read that they both offer fast hybrid AF with suitable lenses and in suitable conditions, yet I'm not convinced they both do when I would expect it.
I first noticed the problem with the Samyang 35mm f2.8, because this has a horrendous amount of focus breathing and the AF hunting it does causes the image to zoom in and out to a very distracting degree, but I have tried it with other lenses too.

On the A7Rii, if I set AF-C then when I focus (by half-pressing the shutter with the camera still as if I were in AF-S), the camera focuses once on the subject, and from then on if I don't change the camera/subject distance the lens either changes focus a tiny amount or not at all. Clearly the PDAF is working.
But in AF-S mode it always goes through the same distracting focus out/focus in/focus back sequence which is clearly CDAF only. It behaves the same way with the 28-70 FE OSS kits lens, though the focus / angle-of-view shift is less distracting.

But if I try the same lenses on the Nex-6 the behaviour is the opposite! In AF-C it always hunts, but in AF-S, it only hunts if I move the camera and if the image stays the same it doesn't hunt (or maybe doesn't re-focus).

I'm still testing behaviour with other lenses (A and E-mount), but what is going on? Why doesn't the Rii use PFAF in AF-S? Why doesn't the Nex-6 use it at all?

Oh, the A7Rii has the latest firmware setting 4.01, the Nex-6 is 1.03. Similar results with the 16-50PZ.

Edited by Miranda F - 19 March 2021 at 20:05
Miranda F & Sensorex, Sony A7Rii, A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras ...
 



Back to Top
QuietOC View Drop Down
Senior Member
Senior Member

Joined: 28 February 2015
Country: United States
Location: Michigan
Status: Online
Posts: 3429
Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 19 March 2021 at 20:04
It might be something specific with that lens. Mine is boxed to sell, but I'll try it out here.

Ok, yeah, that is just normal e-mount focusing. It will always do a contrast-detect flutter in AF-S.

My NEX 5T is acting just like my A7RII in AF-S, but in AF-C it does pulse.

Edited by QuietOC - 19 March 2021 at 20:16
Sony A7RIV NEX-5T HVL-F45RM LA-EA5 Metabones-IV Sigma MC-11 Yongnuo EF-E II TLT ROKR MD-NEX KR-NEX DA-NEX
Minolta Maxxum 600si
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9 AF-P/Q
Back to Top
Miranda F View Drop Down
Senior Member
Senior Member

Joined: 11 January 2014
Country: United Kingdom
Location: Bristol
Status: Offline
Posts: 3847
Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 19 March 2021 at 20:15
Originally posted by QuietOC QuietOC wrote:

It might be something specific with that lens. Mine is boxed to sell, but I'll try it out here.

Thanks, but the behaviour on the A7Rii seems the same on the Samyang 18mm f2.8, the 28-70 OSS and the 16-50PZ.

I also tried A-mount lenses on the Rii with the LA-EA4 and the de-baffled LA-EA1 - as expected both use PDAF in both AF modes, and in AF-S you can see the little green squares light up to tell you where it focussed.
Miranda F & Sensorex, Sony A7Rii, A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras ...
Back to Top
QuietOC View Drop Down
Senior Member
Senior Member

Joined: 28 February 2015
Country: United States
Location: Michigan
Status: Online
Posts: 3429
Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 19 March 2021 at 20:22
The A7III will sometimes show the phase-detect points in AF-S after locking. It doesn't seem like the A7RII ever does that. The NEX 5T never shows the phase-detect points.

FWIW: the FE 35 F1.8 shows the same behavior.

My understanding is that in Fast Hybrid AF all the phase-detect does is give the camera a direction to focus towards. The lens will still always do a contrast-detect hunt. It is not using the phase-detect pixels to confirm focus.

Edited by QuietOC - 19 March 2021 at 20:30
Sony A7RIV NEX-5T HVL-F45RM LA-EA5 Metabones-IV Sigma MC-11 Yongnuo EF-E II TLT ROKR MD-NEX KR-NEX DA-NEX
Minolta Maxxum 600si
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9 AF-P/Q
Back to Top
Miranda F View Drop Down
Senior Member
Senior Member

Joined: 11 January 2014
Country: United Kingdom
Location: Bristol
Status: Offline
Posts: 3847
Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 19 March 2021 at 20:32
Just updated the SEL18-55 to v02 firmware on the Nex-6 and that now shows hybrid AF in AF-S but not AF-C (before it didn't on either)

Looks to me like the Nex-6 only does hybrid AF in AF-S and the A7Rii only does it in AF-C!

I'd be interested in other people's experiences with these and other cameras.

<Sigh> it was all so much easier in A-mount. Either you had PDAF or you had MF.
Miranda F & Sensorex, Sony A7Rii, A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras ...
Back to Top
Miranda F View Drop Down
Senior Member
Senior Member

Joined: 11 January 2014
Country: United Kingdom
Location: Bristol
Status: Offline
Posts: 3847
Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 19 March 2021 at 20:36
Originally posted by QuietOC QuietOC wrote:

My understanding is that in Fast Hybrid AF all the phase-detect does is give the camera a direction to focus towards. The lens will still always do a contrast-detect hunt. It is not using the phase-detect pixels to confirm focus.


That's interesting, but doesn't explain the very different behaviour in AF-S and AF-C. It's as if the Rii remembers where it was focussed in AF-C but forgets it in AF-S, while the Nex-6 does the opposite. Unless there's soemthing else going on I haven't understood.
Miranda F & Sensorex, Sony A7Rii, A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras ...
 



Back to Top
QuietOC View Drop Down
Senior Member
Senior Member

Joined: 28 February 2015
Country: United States
Location: Michigan
Status: Online
Posts: 3429
Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 19 March 2021 at 21:01
Originally posted by Miranda F Miranda F wrote:

Originally posted by QuietOC QuietOC wrote:

My understanding is that in Fast Hybrid AF all the phase-detect does is give the camera a direction to focus towards. The lens will still always do a contrast-detect hunt. It is not using the phase-detect pixels to confirm focus.


That's interesting, but doesn't explain the very different behaviour in AF-S and AF-C. It's as if the Rii remembers where it was focussed in AF-C but forgets it in AF-S, while the Nex-6 does the opposite. Unless there's soemthing else going on I haven't understood.

Yeah, occasionally pointing at stationary object in AF-C/AF-On the motor in the Samyang won't make any noise. The A7III does this even more. They may be doing pure phase-detect in AF-C with native lenses.
Sony A7RIV NEX-5T HVL-F45RM LA-EA5 Metabones-IV Sigma MC-11 Yongnuo EF-E II TLT ROKR MD-NEX KR-NEX DA-NEX
Minolta Maxxum 600si
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9 AF-P/Q
Back to Top
Dyxum main page >  Forum Home > Equipment forums > Camera Talk > E-mount full frame

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.078 seconds.

Monitor calibration strip

Dyxum.com - Home of the alpha system photographer

In memory of Cameron Hill - brettania

Feel free to contact us if needed.