High Dynamic Range (or “HDR”) brings a little professional technique to your iOS 7 photos by taking three exposures with one snap: normal, over, and under. The software then combines these three captures into one optimized photo.
In my experience, HDR-optimized photos in iOS 7 take up an average of .8 megabytes more than their normal counterparts. This doesn’t matter for most of us, though if you have a 16GB device and are trigger-happy with the camera, your space will diminish quicker.
You may turn this feature on and off within the camera app by simply tapping “HDD On/Off” at the top of the screen. You may also choose (in Settings > Photos & Camera) to keep the “normal photo” for every HDR shot you take, effectively having a black sheep twin photo to all your pretty optimized ones.
Some users have complained of their devices “defaulting” to HDR being off upon closing the app and re-opening it sometime later. I’ve discovered that making sure the aforementioned “keep normal photo” feature is off in your settings will keep the HDR setting exactly as you left it (either on or off) next time you open your app.
Give it a shot sometime (sorry for the standard issue pun) and compare the enhanced photo to a normal one to see the difference yourself. Any little thing helps with phone cameras!