TextureFormat.ARGB32 DOESN'T WORK.

Following this page, I implemented a screen capture utility.
http://docs.unity3d.com/ScriptReference/Texture2D.EncodeToPNG.html

PNG file is successfully created when I copy this code directly to my project, but when I use Texture2D of TextureFormat.ARGB32 instead of TextureFormat.RGB24, created PNG Files doesn’t contain any pictures and now it is perfectly transparent.
Do I need any additional code to use ARGB32 TextureFormat? Or it is Unity’s BUG?

Solved. ImageEffect->FXAA is the one which bothered to capture whole 3D into tex.