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Eye start AF ?

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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: Eye start AF ?
    Posted: 24 August 2019 at 21:58
Hello everyone,

I am a bit confused concerning eye start AF.

This question is also valid in A mount APSC actually.

So today I was playing a bit in the park with the A99m2 and minolta 70-210.

Eye-start AF was activated. If I understand well this feature is to optimize AF as soon as we put the eye to the EVF.

But there is something I don't understand:
When my eye is at the EVF, the lens is always AF-ing like if I had half-press shutter in AF-C mode. But the body was on AF-S mode nd I didn't half press shutter.

So why would the AF-motor continuously working back and forth ? Actually I tested shot a static target and the result was better with eye-start AF OFF than ON...

So what is exactly doing eye-start AF ?
 



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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: 24 August 2019 at 22:43
I do not understand your question, why would it not do that? It focuses until You tell it that it has focused on the thing you want it to be focused on: using the half press (or back button). It does not know what you want to focus on.

It is slightly quicker to focus, that is all. Not really necessary for the A99m2. I do not bother.

BTW, do you use AF priority or balanced? Might make a difference!
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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 Posted: 24 August 2019 at 22:59
Thanks for your answer,

I think I wasn't very clear in my first message.

I do understand that the AF can't know what I want to aim at until I half press the shutter.

So question:
Why would the group lens elements moving when you have your eye trhough the EVF without having half-press shutter ? And because of this the AF is going back and forth non stoppely until I half press the shutter... Is it the intended behaviour of eye start AF ?
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 25 August 2019 at 00:02
Originally posted by djfoxy djfoxy wrote:

Why would the group lens elements moving when you have your eye trhough the EVF without having half-press shutter ?

Because Eye-Start AF forces AF-C to be enabled even if you select AF-S. Otherwise it would autofocus only one single time when you first look through the viewfinder. That wouldn't be very good.

And because of this the AF is going back and forth non stoppely until I half press the shutter... Is it the intended behaviour of eye start AF ?

Yes.
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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: 25 August 2019 at 09:55
Originally posted by djfoxy djfoxy wrote:

So question:
Why would the group lens elements moving when you have your eye trhough the EVF without having half-press shutter ? And because of this the AF is going back and forth non stoppely until I half press the shutter... Is it the intended behaviour of eye start AF ?
That is eye focus: it starts focusing as soon as you look through the viewfinder. If you turn it off, it will only start focusing when you half press - I am unsure what you were expecting.

The Beercan is noisy, so, if it moves, it is noticeable. The E-mount cameras do the same, it is called Pre-AF there (why? I do not know), but it is less noticeable as the focus is (almost) silent. When I use the A99m2 with the 70-400G (that one was on the camera), it behaves similar to an E-mount camera as the SSM motor is also quite silent.
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Post Options Post Options   Quote djfoxy Quote  Post ReplyReply Direct Link To This Post Posted: 25 August 2019 at 11:45
Thank you all.

So as an important reminder I'll keep in mind that eye start AF overides any AF mode to AF-C.

 



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SnowFella View Drop Down
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Post Options Post Options   Quote SnowFella Quote  Post ReplyReply Direct Link To This Post Posted: 25 August 2019 at 12:04
Only until you half press the shutter button, then it's AF-S and locks.
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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 Posted: 27 August 2019 at 12:44
Originally posted by SnowFella SnowFella wrote:

Only until you half press the shutter button, then it's AF-S and locks.


Understood. Well I will be better off of eye start AF if I'm shooting stills anyway
For anything moving will be great.

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