HI.
You could test with GetPreviewBufferYCbCr which give you the preview in native format (NV12)

Code:
int layersize = (int)(camera.PreviewResolution.Width * camera.PreviewResolution.Height );
int layersizeuv = layersize/2;
buffer = new byte[layersize + layersizeuv];

var previewBitmap = new Bitmap(
	camera.PreviewResolution,
	ColorMode.Yuv420Sp,
	new uint[]{(uint)camera.PreviewResolution.Width,(uint)camera.PreviewResolution.Width},
	new IBuffer[] { buffer.AsBuffer(0, layersize), buffer.AsBuffer(layersize,layersizeuv) });

	
....
	
	
	
 camera.GetPreviewBufferYCbCr( buffer);