HDR – High Dynamic Range – photography is a method of achieving a degree of visual detail in highlights and shadows beyond what the camera’s image sensor can record in a single exposure. The HDR processing usually involves combining two or more frames taken at different exposures. This is done on the computer or inside the camera itself. Human vision uses the HDR approach. The dynamic range of your eye is relatively low. Speaking in photographic terms, the visual cortex part of your brain continuously processes multiple frames takes at different exposures to paint a highly-detailed image. The optics of your eye is comparable to a cheap plastic camera. What makes all the difference is the power of your brain.

The iPhone and iPhone 4S can’t compare to a human brain, but do offer a limited automatic HDR mode. The phone takes two photos in a quick succession at slightly different exposures and combines them into a single image that offers greater detail in both highlights and shadows. There are two primary drawbacks of any HDR system. First problem is that combining the photos into one takes time and processing power. The iPhone 4 takes nearly three times as long to make an HDR photo when compared to a standard non-HDR shot. The second problem is the ghosting effect: a brief period of time elapses between the two photos used for the HDR image and during this time the scenery may change slightly. This introduces the ghosting effect, which is exacerbated by low-light conditions, scenery movement and camera shake. iPhone 4’s HDR feature works best with plenty of light, stationary scenery and steady hands.

Below are a few examples of HDR photos taken with an iPhone 4S using built-in HDR functionality, as well as a couple of popular HDR apps. For reference we also included a couple of photos of the same scenery created using a Canon G10 and computer HDR-processing software.

Setup

A tripod-mounted iPhone 4S and a tripod-mounted Canon G10. The still-life scenery featuring wide range of highlights, shadows and reflections. Post-processed in Photoshop by a professional photographer to achieve the best quality for each image.

iPhone 4S

Below: non-HDR photo

Below: using built-in HDR feature of the iPhone

Below: an HDR shot using the Pro HDR app in automatic mode with two exposires

Below: an HDR shot using True HDR app in automatic mode with three exposures

Canon G10

Below: non-HDR photo

Below: HDR photo using three exposures at 0+/- 1/2

Instead of a conclusion

In my view, the best HDR result for the iPhone was achieved by True HDR app in this case. The Pro HDR app overexposed the final image. The built-in iPhone HDR logic underexposed it. The best photo overall is the Canon G10 non-HDR shot. But, of course, we are not comparing a cell phone to a high-end portable camera.

HDR is an interesting and useful feature that can produce excellent results under certain conditions. The main problem with iPhone’s HDR is ghosting. The phone’s processing power is insufficient to eliminate the ghosting effect in a reasonable amount of time. And the small and slippery form of the phone ensures there is plenty of camera shake when you take photos.