When to use HDR
Landscapes: A classic use of HDR in regular photography is on landscape shots with a bright sky above the horizon line and darker foreground below. iPhone 4 users who want to bring out more details in both parts of a landscape shot should turn on the HDR mode. One area that the iPhone’s HDR mode falls short is sunsets. In its attempt to lighten up the over-exposed sun, it also loses some of the beautiful red and orange coloring that makes the scene so stunning in the first place
Outdoor portraits: The midday sun’s harsh light usually makes for unflattering portraits. It can cast strong shadows on a person’s face and create dark circles around the eyes. It also bounces off of skin and accentuates shiny spots. The iPhone’s HDR setting can minimize the effect of these two extremes and create a more evenly lit portrait.
However, if the subject is completely back lit, the limited powers of HDR mode might not be enough to brighten their face. To shoot a usable back-lit portrait, first tap to focus on the darkest part of the person’s face. The background will become extrememly blown-out. After you take the shot, the final HDR photo will combine the properly exposed person with a slightly toned town background. (Many photographers use a fill flash in back lit portrait situations, but unfortunately the iPhone’s auto mode adjusts for the presence of the flash and skews too dark.)