It's unfortunate that HDR mode in Google Camera remains unavailable for phones other than the Nexus 5 & 6 -- I have a Moto X, and the app is really only useful for photospheres, since normal photos tend look awful without HDR.
Has Google discussed any technical reason for this restriction? Seems like lots of third party apps support HDR on a wider variety of phones...
Google's HDR+ is different from regular HDR, which can be acheived through burst exposure bracketing and computation alone. HDR+ also performs stabilization and other tricks to improve the result, and these operations might depend on additional hints from the hardware to acheive the desired accuracy. OEMs are free to implement such features in their own apps, specialized to their own hardware, and most in fact do.
HDR+ is available only on Nexus 5 and Nexus 6, because only those devices currently fully support the Camera2 API, which is required for HDR+. This will gradually change, and more devices will start offering it.
Lens Blur is pretty great, too, and it's available for others. I think the restriction may be the fact that it has to 1) support OIS and 2) Google has to support that specific OIS.
It would be nice if Google could do something similar for EIS phones, too, though.
Has Google discussed any technical reason for this restriction? Seems like lots of third party apps support HDR on a wider variety of phones...