Improve AVCaptureVideoPreviewLayer performance when capturing in photo quality
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I am working on augmented reality app, the main feature of which is to show the overlay over the camera preview, but I also need to be able to save the high resolution photo with the overlay applied. 
For this purpose I set up the `AVCaptureSession` with preset set to `AVCaptureSessionPresetPhoto`. But the smoothness and responsiveness of AVPreviewLayer for such session is much worse then for preset `AVCaptureSessionPresetHigh`. At the same time the area which is shown in preview with `AVCaptureSessionPresetHigh` preset is smaller than with `AVCaptureSessionPresetPhoto`. But that is not that important for me.

So the question is how to capture the photo in high quality from the camera, but have the same  level of responsiveness of previewLayer as in case of video capture?