iOS: AVCaptureStillImageOutput gives bad image output - ios

Question

I am programmatically launching camera using AVCaptureVideoPreviewLayer and then using the following code to take picture automatically. Output of the picture is not good resolution and brighter than how we normally use native camera and take pictures. What is the problem here, could someone help?
-(void) capturePicture
{
// Get all cameras in the application and find the frontal camera.
AVCaptureDevice *backCamera;
NSArray *allCameras = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
// Find the back camera.
for ( int i = 0; i < allCameras.count; i++ ) {
AVCaptureDevice *camera = [allCameras objectAtIndex:i];
if ( camera.position == AVCaptureDevicePositionBack ) {
backCamera = camera;
}
}
// If we did not find the camera then do not take picture.
if ( backCamera != nil ) {
// Start the process of getting a picture.
AVCaptureSession *session = [[AVCaptureSession alloc] init];
// Setup instance of input with back camera and add to session.
NSError *error;
AVCaptureDeviceInput *input =
[AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error];
if ( !error && [session canAddInput:input] ) {
// Add frontal camera to this session.
[session addInput:input];
// We need to capture still image.
AVCaptureStillImageOutput *output = [[AVCaptureStillImageOutput alloc] init];
// Captured image. settings.
[output setOutputSettings:
[[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG,AVVideoCodecKey,nil]];
if ( [session canAddOutput:output] )
{
[session addOutput:output];
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in output.connections) {
for (AVCaptureInputPort *port in [connection inputPorts]) {
if ( [[port mediaType] isEqual:AVMediaTypeVideo] )
{
videoConnection = connection;
break;
}
}
if (videoConnection)
{
break;
}
}
// Finally take the picture
if ( videoConnection )
{
[session startRunning];
[output captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)
{
if (imageDataSampleBuffer != NULL)
{
NSData *imageData = [AVCaptureStillImageOutput
jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *photo = [[UIImage alloc] initWithData:imageData];
UIImageWriteToSavedPhotosAlbum(photo, nil, nil, nil);
[session stopRunning];
NSInvocation *myInvocation = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:#selector(endScreen)]];
[myInvocation setSelector:#selector(endScreen)];
[myInvocation setTarget:self];
appDelegate.bImageTaken = YES;
UIImageWriteToSavedPhotosAlbum(photo, nil, nil, nil);
[NSTimer scheduledTimerWithTimeInterval:0.5 invocation:myInvocation repeats:NO];
}
}];
}
}
}
}
}