AVCaptureSession preset photo and AVCaptureVideoPreviewLayer size

Question

I initialize an AVCaptureSession and I preset it like this :

AVCaptureSession *newCaptureSession = [[AVCaptureSession alloc] init];
if (YES==[newCaptureSession canSetSessionPreset:AVCaptureSessionPresetPhoto]) {
    newCaptureSession.sessionPreset = AVCaptureSessionPresetPhoto;
} else {
    // Error management
}

Then I setup an AVCaptureVideoPreviewLayer :

self.preview = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height/*426*/)];
CALayer *previewLayer = preview.layer;
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
captureVideoPreviewLayer.frame = previewLayer.frame;
[previewLayer addSublayer:captureVideoPreviewLayer];
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspect;

My question is:
How can I get the exact CGSize needed to display all the captureVideoPreviewLayer layer on screen ? More precisely I need the height as AVLayerVideoGravityResizeAspect make the AVCaptureVideoPreviewLayer fits the preview.size ?
I try to get AVCaptureVideoPreviewLayer size that fit right.

Very thank you for your help

Answer 1

After some research with AVCaptureSessionPresetPhoto the AVCaptureVideoPreviewLayer respect the 3/4 ration of iPhone camera. So it's easy to have the right height with simple calculus.
As an instance if the width is 320 the adequate height is:
320*4/3=426.6