Does Xperia S support HDR?
HDR has not to be enabled on the device. It is a software feature, combining multiple photos (see: Bracketing) into one. So you will need a camera app supporting this.

AFAIK the stock camera shipping with Android 4.2+ does so, plenty more are available on Google Play (not necessarily requiring Android 4.2+, most will run on your device). See e.g. Camera HDR Studio or HDR Camera for apps explicitly dedicated to this feature, or Camera FV-5 for an all-round-camera having this feature "amongst others". More to find out there.

A helpful article to read on the topic: How to use HDR on your Android device.