void RemoveObservers ()
{
subjectAreaDidChangeToken.Dispose ();
runtimeErrorToken.Dispose ();
wasInterruptedToken.Dispose ();
interruptionEndedToken.Dispose ();
runningToken.Dispose ();
focusModeToken.Dispose ();
lensPositionToken.Dispose ();
exposureModeToken.Dispose ();
exposureDurationToken.Dispose ();
isoToken.Dispose ();
exposureTargetBiasToken.Dispose ();
exposureTargetOffsetToken.Dispose ();
whiteBalanceModeToken.Dispose ();
deviceWhiteBalanceGainsToken.Dispose ();
}