We've been wondering what that second camera on the back of the HTC M8 (a.k.a. "The All New HTC One") was all about since the first leaks arrived. If an Australian Telstra ad for the new device is to be believed, it is indeed intended to bolster the phone's low-light shooting performance. The advertisement spotted by GSMArena reveals a few things that we didn't already know, and it does indicate that the "Duo Camera" can "create vivid images even in low light."
Low light photography is always tricky, and it's particularly difficult on mobile cameras thanks to their generally small sensors and lenses.