The Duo camera is one of the distinguishing features of the HTC One M8 – it makes it possible to re-focus the picture after you’ve taken it (this is a Duo effect called U-Focus). In a sense, it simulates a shallow depth of field that you would get from a DSLR and a fast lens.
From a technical standpoint, there are some phones/camera apps that simulate this effect with a regular (i.e. single lens camera), but none come close to the quality that the One M8 produces with it’s multiple simultaneous captures. And actually the resulting images from the M8 look quite nice in my opinion.
HTC has also added some new Duo effects since the initial release of the phone (let’s call these enhancements “Duo effects v2”). One is the ability to control the blur strength of out-of-focus areas of the photo. The other is an effect called “Foregrounder” that works similar to U-Focus except it applies an artisitic filter to the out-of-focus area to further highlight your subject.
The trouble for people who like to use custom ROMs is that many non-stock (Sense) based ROMs break the Duo camera because the camera drivers do not capture the necessary additional photographic data to make post-processing possible. Here’s a compatibility matrix to figure out if you’ll be able to use Duo camera effects like U-Focus:
|Duo effects v1||Duo effects v2|
|Google Play Edition KitKat 4.4.4||Yes||Yes (with HTC Gallery update)|
|Google Play Edition Lollipop 5.0||Yes||Yes (with HTC Gallery update)|
|Google Play Edition Lollipop 5.1
Stock GPE download
|Any AOSP-based ROM||No||No|
|Any Sense-based (stock) ROM||Yes||Yes (with HTC Gallery update)|
Please note that if you do not see the HTC Gallery app available in your Play Store, you can download the latest version using APK mirror:
There are also a couple recovery-flashable ZIPs out there of the Sense 7 camera and gallery APKs (like this one by digitalhigh on XDA, for example). And while they do properly install the HTC Camera and Gallery on any ROM (i.e. AOSP based, CM12 based), they do not seem to actually support the Duo Camera and effects properly – so you’ll get the nice HTC UI but no ability to do U-Focus or foregrounder effects.