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a900 vs a99ii Auto Focusing

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Roger Rex View Drop Down
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Post Options Post Options   Quote Roger Rex Quote  Post ReplyReply Direct Link To This Post Topic: a900 vs a99ii Auto Focusing
    Posted: 26 September 2021 at 11:06
I shoot regularly with the a900 and a99ii. There is one demonstrable difference in their auto-focusing capabilities. The a900 clearly is easier, requiring far less contrast in the scene at the point of focus (the center square). I was shooting with both a lot the last two days and this became a point (a pun of sorts) of frustration with me when using the a99ii on the same subject. Has this difference been seen by you? Is it possibly a problem with my a99ii?

The frustration is compounded by the ultra-sensitive toggle button on the a99ii. I shoot using a tripod extensively and use back button focus. The a99ii toggle is ludicrously sensitive, much more difficult to press straight in without it going off to the side, i.e., moving the auto-focusing square hither and yon. Gary Friedman mentioned this early on, thinking his then new a99ii must be damaged. Does anyone know of a way to de-sensitize the toggle?
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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: 26 September 2021 at 12:39
I find 79-point SLT AF sensor is not as sensitive as the 15-point sensor. Sony AF processing seems to benefit from those extra points though. If you like to use a single AF point especially the center one, the older cameras will likely work better.

The A900 has a dual cross type sensor and an F2.8 sensor in the center. I believe the F2.8 sensor is only a line type.

The on-sensor phase-detect of the A99II/A7RII/III isn't great either though it is much better than that of the A99/A7/A7II.

Edited by QuietOC - 26 September 2021 at 12:47
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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: 26 September 2021 at 13:08
Yep, the double cross of the A900 is better then any of the focus points of the A99m2 with or without the on-sensor AF activated. If there is anything moving, the A99m2 is better. That central focus point was an important reason I was not interested in the A99.
I use Expand Flexible Spot with the A77m2 and A99m2, the extra focus points help with the pick-up. It is about as good as the A900 in my use (YMMV).

Re. your other problem: you can assign a different button to do the back button focussing: the AEL or af/mf buttons are nicely placed as well. And if you use it on a tripod, it is even not that important where the button is placed. Easy.

Edited by addy landzaat - 26 September 2021 at 13:12
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Post Options Post Options   Quote Roger Rex Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2021 at 11:09
Thank y9u both for the help. Kind of good news, bad news - my a99II is not defective (good news) but the problem of the less efficient auto-focusing for my shooting needs is permanent (bad news). Good news - addy has provided a workaround for the finicky toggle (thanks).
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Post Options Post Options   Quote Jonas A-R Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2021 at 12:38
Originally posted by addy landzaat addy landzaat wrote:

Yep, the double cross of the A900 is better then any of the focus points of the A99m2 with or without the on-sensor AF activated.


The problem is of course that your point of focus rarely is dead center. As soon as you swing the camera to recompose you will throw whatever was in-focus out of focus. It might be a minor issue if you have sufficient DoF, but not so good for critical work.
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Post Options Post Options   Quote Roger Rex Quote  Post ReplyReply Direct Link To This Post Posted: 27 September 2021 at 13:22
Originally posted by Jonas A-R Jonas A-R wrote:

The problem is of course that your point of focus rarely is dead center. As soon as you swing the camera to recompose you will throw whatever was in-focus out of focus. It might be a minor issue if you have sufficient DoF, but not so good for critical work.


Correct. It so happens that my center focus and re-compose regimen is used when shooting, typically at f16. If a different scenario, the a99ii with its many focus points overcomes the problem you describe.
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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: 28 September 2021 at 11:09
Did you try expand flexible spot? It might make a difference.
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Post Options Post Options   Quote Roger Rex Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2021 at 11:40
Originally posted by addy landzaat addy landzaat wrote:

Did you try expand flexible spot? It might make a difference.


Thanks, I was not familiar with this option. I just read the description in the manual and will definitely experiment with this. The flexible spot option, if I am interpreting the manual correctly, seems to do automatically what I now do manually, i.e., move the center focus square to the closest high-contrast area that is in or almost in the same focus plane, an imprecise method when done manually.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2021 at 13:56
This is what is quite nice about the latest mirrorless bodies: Real-time Tracking. There are various ways to initiate the focus tracking. One of the easiest is to select center area, then whatever object is in the center at the initial shutter half-press/AF On continues to be tracked by all the AF points.

The old Object Tracking tried to do something similar but it requires more buttons to initiate.

Edited by QuietOC - 28 September 2021 at 13:59
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