Force AE to strictly respect MeteringPoint

[Nathan AUDVARD]

Hi,

I'm working with CameraX and implementing a custom AE zone using FocusMeteringAction.

I've noticed that the AE algorithm seems to look outside the zone, I think to avoid burning some part of the picture. However, for my use case, I need the exposure to be optimized strictly for the content inside the AE zone. I do not mind if the rest of the image is overexposed.

I'm using CameraX 1.5.2.

Is there a way to force AE to ignore the outside region ?

Thanks!

[Tahsin Masrur]

Hi,

I guess this matches with the feature request issue we have created at https://issuetracker.google.com/issues/477810106?

I don't think there's any easy way to do this for users with the current public APIs of CameraX, we will need to add a new API. Just from the top of my head, I am thinking it can be new overloads of the FocusMeteringAction.Builder#Builder and FocusMeteringAction.Builder#addPoint functions which accept a `lockingMode` in addition. For example,

```

cameraControl.startFocusAndMetering(
    FocusMeteringAction.Builder(
            point,
            lockingMode = FLAG_AF or FLAG_AE or FLAG_AWB // Default is just FLAG_AF

        )
        .build()
)
```

What do you think? Does this satisfy your requirements?

[Nathan AUDVARD]

Thanks for the quick reply. 

Actually, my requirement is spot metering. The current implementation seems to act like matrix/evaluative metering (taking the rest of the scene into account), whereas I need the exposure to be calculated solely based on the metering point.

[Scott Nien]

Will using a smaller size for the MeteringPoint work for you? 

When constructing the MeteringPoint,  you can specify an additional size parameter (0.. 1.0f)
Like the following:

factory.createPoint(e.getX(), e.getY(), 0.1f).  //Default size is 0.15f 

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