Application.CaptureScreenshot() renders black pngs.

Hi:

I am trying to render a scene and export the image sequence from the main camera. I used the following code:

 void LateUpdate ()
 {

     string name = string.Format("{0}/{1:D04} shot.png", folder, Time.frameCount);

     Application.CaptureScreenshot(name);
 }

The script only renders proper images in the following condition:

1. Build and run the game, resolution at less than 1920x1080 at full screen. (windowed, or 1920x1080 will result in black image)

2. Click play button in Unity Game View, when the quality setting's anti-alias is turned off. (anti-alias turned on will result in black images)

Is this a bug? or am I doing things wrong?

Unreal Engine does amazing job for realtime rendering, easy to use and fast to render. How do I achieve this in Unity??

Thanks