Camera [Q] Taking pictures and combing them later to HDR

On Google Play is many many HDR apps, some bad, some good.

Every app essentially works like this (when you press the take a picture button):
1. it takes pictures with EV -2.0, then
2. it takes pictures with EV +-0.0, then
3. it takes pictures with EV +2.0, then

4.it combines all three pictures

The first three steps on my phone (Xperia Miro) took about half the second; but last step takes forever (about 15 seconds) and it doesnt look good. If I combine those 3 pictures with PhotoShop combined picture look stunning
My question is; is there some app that can do all 3 steps or is there some app that can do all 4 steps with option to disable 4 step.