[Unity2D] How to apply filter in Sprite?

I want to apply Filter to a Sprite. and then be able to modify the opacity of the filter during runtime. How should I do it? I tried changing the Sprite Renderer’s color but it doesn’t give me the desired effect.

Please see attachment to see what I want to achieve. Thanks!!

[21610-screenshot+2014-02-03+04.16.41.png|21610]

[21611-screenshot+2014-02-03+04.16.16.png|21611]

It’s very easy to do when using a mask sprite, here is a screenshot that explain how this is done, and as you might notice the filter is there but it’s also affecting the gray area, which can easily be fixed by creating the correct size-shape mask
good luck