HTC One M8 - Manual (Page 66)

Lighting
§ Use Duo Camera in an environment where there is a good light source. Post-
processing effects for Duo Camera do not work for low light photography or
when you're using the camera flash.
§ If lighting is uneven, like when the background is a little bit under or
overexposed, tap
to adjust the exposure settings.
§ Hold HTC One so that you don't block the second camera lens.
Composition
§ Match your subject with an interesting background. Positioning your subject
with some lights or a garden in the background will add color and distinction to
your photo, especially if you'll use the UFocus
™ feature in Gallery.
§ Post-processing effects for Duo Camera may not work if your subject and
background are too close or when you're taking a close-up shot. So, mind the
distance between your subject and your background, as well as the distance
between the camera and your subject.
1 m ~ 2 m
66 Camera