title: AVFoundation video preview is darker than the native Camera app
body: <p>I am using AVFoundation to produce video frames.
  The problem is that the frames look darker than in the native camera app, especially in dark areas.</p>
  
  <p>As I see, the native camera app (iOS 8) makes some adjustments (ISO, shutter speed) all the time and continuously adopts itself to the environment light conditions (it seems that in low-light conditions it slows the shutter speed, rather then increasing the ISO).</p>
  
  <p>I cannot make my video preview looks the same. Tried settings the exposure mode to AVCaptureExposureModeContinuousAutoExposure, but it does not make the same effect. </p>
  
  <p>Please advise     </p>