dont know why they did it this way, but apparently when you flash CM10.1 you get the camera with HDR, and when you flash the 12/12 GAPPS, it overwrites the camera with the stock AOSP one which doesn't include HDR.
there are ways around it, you can install the CM10.1 camera side by side with the stock camera (because you loose photosphere with CM camera) by pushing it system/app and changing permissions.
but to be honest, i installed it, and the results were TERRIBLE. i tried holding it as steady as possible (using my desk as a "tri-pod") and it still came out SUPER blurry. maybe with some further away HDR shots it might have worked better, but i didn't even try any of those. something like HDR camera gave me better results, and it wasn't any more of a pain because it still had to have 2 camera apps on my phone.
either way, hit the link below for the gallery2.apk
use root explorer or equivalent and push to system/app and change permissions to what all the other apps are, reboot and enjoy.
http://dl.dropbox.com/u/20875109/Gallery2.apk
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