Preview using Auto AE mode while capture using manual AE - is it possible?

[László Heller]

Hi!

My goal is to create a camera app which is able to take pictures using manual ISO and shutter speed settings. In other words manual AE.
When I change my preview builder's settings, the preview picture is blank and I cannot take picture:

var pb = new Preview.Builder();
var ext1 = new Camera2Interop.Extender(pb)
        .SetCaptureRequestOption(CaptureRequest.ControlAeMode, (int)ControlAEMode.Off)
        .SetCaptureRequestOption(CaptureRequest.SensorSensitivity, 400)
        .SetCaptureRequestOption(CaptureRequest.SensorExposureTime, 100000000); // 100 000 000 ns = 100 000 us = 100 ms
var preview = pb.SetTargetName("PREVIEW").Build();
preview.SetSurfaceProvider(sfcPreview.SurfaceProvider);

The same, when I keep auto AE settings for preview and use manual AE for capture:

var cb = new ImageCapture.Builder();
var ext2 = new Camera2Interop.Extender(cb)
        .SetCaptureRequestOption(CaptureRequest.ControlAeMode, (int)ControlAEMode.Off)
        .SetCaptureRequestOption(CaptureRequest.SensorSensitivity, 400)
        .SetCaptureRequestOption(CaptureRequest.SensorExposureTime, 100000000); // 100 000 000 ns = 100 000 us = 100 ms
capture = cb
        .SetTargetResolution(new Size(800, 600))
        .SetTargetName("CAPTURE")
        .Build();

So my question is: How to properly configure preview for auto AE and at the same time capture for manual AE or whether it is possible at all?

BR,

Ladislav

[Scott Nien]

Hi Ladislav,

Currently CameraX doesn't support setting camera2 parameters only for still capture.  The parameters you set in the ImageCapture will actually apply to the whole repeating request (hence the preview)

I may miss something but I think ensuring preview and still capture have similar camera output is quite important for users to see what they will get before capturing. 

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[László Heller]

Hi!

OK, but when I try to set manual settings only for preview, I get only blank/black screen in app's preview surface.
See the lines 84-91 of the IRunnable.Run() method:

When I comment out the lines 86-89, the preview (and also take picture) works well.

So how to enable manual exposure correctly in CameraX ?
BTW my device is Samsung Galaxy S20+ which supports manual mode!

BR,

Ladislav

[Scott Nien]

I tested it with the same manual AE parameters you set on Galaxy Z Fold2 and Pixel 6 and I can see the preview (it's a little bit over-exposed). 

I think this is probably the Galaxy S20+ issue.  Can you try adjusting the parameters ? 

[László Heller]

Can U please share your FULL code?
It is really annoying that it doesn't work for me. Tried also change the parameters, but the result is same: Blank/black preview screen.

[Scott Nien]

I modified the CameraXBasic at https://github.com/android/camera-samples/tree/master/CameraXBasic

My modification is to replace the following block 

 preview = Preview.Builder()
                // We request aspect ratio but no resolution
                .setTargetAspectRatio(screenAspectRatio)
                // Set initial target rotation
                .setTargetRotation(rotation)
                .build()

with 

        val pb = Preview.Builder()
                // We request aspect ratio but no resolution
                .setTargetAspectRatio(screenAspectRatio)
                // Set initial target rotation
                .setTargetRotation(rotation)

        Camera2Interop.Extender(pb)
                .setCaptureRequestOption(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_OFF)
                .setCaptureRequestOption(CaptureRequest.SENSOR_SENSITIVITY, 400)
                .setCaptureRequestOption(CaptureRequest.SENSOR_EXPOSURE_TIME, 100000000) // 100 000 000 ns = 100 000 us = 100 ms

        preview = pb.build()

And if I understand it correctly,  you were using Xamarin .  I am not sure if something went wrong with Xamarin. 

Scott

[László Heller]

Hi!

Yes, I am using Xamarin. BTW the problem was solved. Don't ask why, but for sensor exposure time value I have to tell explicitly that the value is a long.

So instead of
.SetCaptureRequestOption(CaptureRequest.SensorExposureTime, 100000000)

I had to call
.SetCaptureRequestOption(CaptureRequest.SensorExposureTime, 100000000L)

...and it works!

BR,

Ladislav

[Scott Nien]

Hi Ladislav, 

Very interesting.  You actually identified one potential issue of camera2Interop API. 

I realize that if you use  

     new Camera2Interop.Extender(pb)  

instead of  

     new Camera2Interop.Extender<>(pb)

The value type checking is ignored by the compiler somehow.   

If you use the new Camera2Interop.Extender<>(pb) and try to set an int to the Long key,  it will build fail.