Hi ,
I was wondering about two things,
* Is there a way to scale from the center in the tranform tool. It scales from a corner everytime.
* What is the best way to give a lens distortion to my entire image with all layers. I have tried the warp and deform brush with not much success.

Thanks in advance.

Scale from the "tool options" docker.

For post processing I would use Blender's compositing editor, it has lens distortion, chromatic aberration, vignetting, etc. nodes.

Thanks Charblaze,
I tried the Tool Options and it does move the pivot to the center but the scale doesn't happen from center while holding shift. Similar thing is mentioned in this thread
viewtopic.php?f=139&t=111701

And I will have to look into Blender compositing keenly.