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LAEA-4 What is its AF system coming from?

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djfoxy View Drop Down
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Post Options Post Options   Quote djfoxy Quote  Post ReplyReply Direct Link To This Post Topic: LAEA-4 What is its AF system coming from?
    Posted: 10 August 2022 at 21:24
Hello there,

I am using a lot (and logically) the LA-EA4 with my A7m1 and it made me wonder something I never thought about:
What is the AF system in LAEA4 coming from?

I mean it's essentially the same AF I have in my A58 camera but thinking further I say: the A58 is an APSC camera. The FF camera of this period of time was the A99v.

So why didn't Sony implement the A99v AF system in the LA-EA4 FF adapter AF system?
Can I conclude that Sony did just a copy/paste of LAEA-2 with the measurements to fit FF?
 



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QuietOC View Drop Down
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2022 at 22:18
The A99 used the same AF sensor as the A77, so not really specifically full-frame either. I haven't used either of these.

Or maybe you are asking why the SLT adapters don't implement AF-D or Hybrid-AF like the A99 models?

I do find the 15-point sensor used in the LA-EA2/4, A33, A35, A37, A55, A57, A58, A65 can distinguish depth better than the 79-point sensor in the A68, A77II, A99II.

And the 79-point sensor is so much better than on-sensor AF points. At least for the cameras I've had so far.

Maybe there was not enough bandwidth in the original E-mount interface to handle more AF points.

Edited by QuietOC - 10 August 2022 at 22:27
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
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addy landzaat View Drop Down
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2022 at 22:41
It is the system of the A77/A65 - the best system when the LA-EA2 was introduced. When the LA-EA4 was introduced Sony clearly felt the 15-point AF system was good enough.

The A99m2 used the 79-point AF-sensor in combination with the on-sensor phase detect points resulting in an impressive AF-system with basically 79 cross points with Sony lenses. It is better then the system in the A77m2. I never used the 15-point AF-system, but had no complaints with the 79-points in my A77m2.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2022 at 01:47
The A77 had a 19-point sensor that was later also used in the A99. 11 cross points, instead of just 3 in the 15-point sensor.

The A65 used the 15-point sensor that was already used in the previous SLTs and the A580/A560 SLRs.

Edited by QuietOC - 11 August 2022 at 02:03
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
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Post Options Post Options   Quote 4paul Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2022 at 04:13
djfoxy you are correct, the "full frame" EA4 adapter has the APS-C AF module. As addy and QuietQC said it was the same with the a99 camera which had the AF module from the a77, David Kilpatrick on PhotoClubAlpha did a big blog post years ago describing it.

So Sony saved money and R&D cost with the copy/paste. At the time nex and APS-C cameras were not "professional" so the thinking could have been: Only "professionals" use AF points outside the center, most people only use the center AF points so why give them AF points they won't use!?

The EA4 adapter has a larger window with less baffle, to fit the image circle of full frame. Otherwise I don't know of any difference between the EA2 and EA4 adapters, they should be identical other than the baffle and firmware to identify "crop mode", although Sony did tighten the mount tolerances after the first few NEX cameras so maybe the metal mount ring is different also (I'm not at home to compare mine).

Interestingly, the "Monster Adapter" EA4r circuit board allows focus points outside the APS-C module, since it removes the circuit board with the AF logic and replaces it with firmware and a board which uses the camera on-sensor AF points, and uses the screw-drive AF motor for Minolta/Sony lenses, with some limitations and a warning about changing lenses https://www.dyxum.com/dforum/laea4r-monster-adapter-v02_topic138642.html
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2022 at 12:36
Also note that the outer 18 points of the 79-point sensor are not used with many full-frame lenses like the old SAL75300.

Native emulating adapters on E-mount cameras only get phase-detect in a central region of the sensor. Sigma's old native E-mount APS-C F2.8 primes have this limitation too. This is a smaller region that covered by the 15-point sensor.

Something is required to get off axis phase detect to work well.

Edited by QuietOC - 11 August 2022 at 12:50
Sony A7RIV LA-EA5
Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9
 



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addy landzaat View Drop Down
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2022 at 12:53
Originally posted by QuietOC QuietOC wrote:

The A77 had a 19-point sensor that was later also used in the A99. 11 cross points, instead of just 3 in the 15-point sensor.

The A65 used the 15-point sensor that was already used in the previous SLTs and the A580/A560 SLRs.
My bad, I thought the A65 and A77 had the same AF system. Knew it was the A65 one.
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Post Options Post Options   Quote djfoxy Quote  Post ReplyReply Direct Link To This Post Posted: 13 August 2022 at 20:55
Didn't know this specifics. And curious for native lens...
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