The HTC Butterfly S can shoot videos at up to 1080p resolution at 30fps. It has an HDR option for the video, but note that the frame rate falls to 28fps, if you enable it and the field of view gets narrower in this mode. It also supports 720p @ 60fps high framerate video recording.
The camera features continuous autofocus and you have the option to lock the focus during video recording, if it hunts too much in dynamic scenes.
Videos are recorded in MP4 files with a solid 21Mbps bitrate - among the highest we've seen. Sound is captured in stereo with 192Kbps bitrate and 48kHz sampling rate. For the most part, framerates were solid at 30fps, but sometimes would dip to around 28fps depending on what you're shooting.
Other than that, videos provide better quality than still images, with good color reproduction and not too much noise.
Here is a FullHD video sample captured with the Butterfly S we uploaded to YouTube.
You can also download an untouched 1080p sample (0:15s, 38.5MB) taken straight off the HTC Butterfly S.
You can also watch a video shot with the HTC One a minute after the video above:
HDR videos capture more detail in the highlights, but don't do much for the shadows. The white balance is off (videos have a purple tint) and the colors are duller. Combined with the narrower FoV, we'd only enable HDR for videos as a last resort when shooting against the sun.
Here's a 1080p HDR sample as well.
There's a 60 frames per second mode on the HTC Butterfly S but it reduces the maximum resolution to 720p. This doesn't sound too bad, but the actual output is pretty bad. There's very little detail and even though the clips are really smooth, we'd advise you to stay away from this mode. Oddly, we found that the 720p @ 60fps mode has the widest FoV, wider than even 1080p with HDR off.
Overall image quality is nearly identical to the HTC One, although the lack of OIS means you can't get steady hand-held videos and that makes quite a lot of difference.
We've added the HTC Butterfly S to our video quality comparison tool. Here it really managed to show what it's capable of, particularly when you look at the low-light video where it easily trashed its competitors (we use a tripod though).