





Amateur and professional iPhotographers have a little-known tool in their mobile belt. The iPhone 4 offers "HDR" functionality that can help you get the most out of the phone's built-in camera.

Here we take an in-depth look at the feature and offer advice for when it's best to use it and — just as importantly — when it's not.

Have a look through these tips and let us know in the comments how you put your photography talents to use.

What is HDR?







"High Dynamic Range" (HDR) Imaging is the practice of using "exposure bracketing" to create an image with a better representation of light and dark areas than the camera could capture on standard settings.

Used correctly it will create an image that's more akin to what your eye — which more efficiently processes extremes of light — would see, rather than what the camera's sensor can photograph.

Typically this is done by capturing three images — a standard exposure, a shot that is one exposure stop too light and a shot that's one exposure stop too dark — and then combining all three.

HDR on the iPhone

In its HDR mode, the iPhone 4 automatically recreates this process by taking three photos at different exposure levels, then layering the shots together to create one image with (theoretically) the best elements of each.

You can turn on the HDR functionality of your iPhone when in the camera by tapping the HDR icon at the top of the screen.







With HDR set to "on," your iPhone will capture the original image and an HDR version, both of which you'll find saved in your Camera Roll. You can change your iPhone's settings to discard the original image but we find it useful for comparisons.







If it's not obvious to you which is the HDR image, look for the HDR icon at the top of the screen above the photo.







DO Use HDR...

Here are three scenarios for when hitting up that HDR button would be a good idea.

... When There's Strong Backlight







In the non-HDR image above you can see very little detail in the shadow as the camera has not coped well with the bright light coming from the doorway. The HDR pic has much more even lighting overall and shows significantly more detail. This will also be the case if you're photographing a light object against a dark background.







...For Landscapes







Here you can see the HDR functionality has handled the contrasts of sunlight and shadow much better than the non-HDR image above. The foreground is severely bleached out in the original image and the areas of shadow much darker. The HDR setting has fixed these issues. You will also find that HDR adds detail to the sky where the standard camera would struggle with the contrast between the sky and the land.







... For Portraits in Strong Sunlight

Strong sunlight is not great for portraits as it can create harsh shadows and unflattering glare. In this self-portrait you can see that the skin tone has been evened out, the glare on the cheeks improved and the shadow cast by the hat made softer.

DON'T Use HDR...

There are some situations in which HDR is actually a hindrance rather than a help. Here are three to be aware of.

...If There's a Risk Your Subject Will Move







Because the iPhone snaps three pics consecutively, if anything in the frame moves (or if you're not holding the iPhone steady enough) you're likely to end up with a blur or ghosting in your image. In our example images you can see that even though the three HDR images are taken milliseconds apart, just a slight breeze moving the buttercups was enough to spoil the shot.







...If You Want Strong Contrast







HDR takes extremes of light and creates a middle ground. This can be great in many scenarios but not if you want to capture striking contrasts. Here we wanted to capture the vibrant green leaves against the lighter foliage in the background and the brightness of the sky. The non-HDR image (above) has achieved this much better than the HDR snap below, in which the light has been toned down and the background detail filled in for an overall muddier final shot.







...If You Want Vivid or Accurate Colors







The iPhone's camera generally deals well with color, giving nicely saturated results. Add in HDR however, and the colors you see in the final image aren't likely to be true-to-life, or particularly vivid. In these images you can see the non-HDR photo above has bolder colors while the HDR shot below has darkened some tones and dulled the effect.







In Summary

The iPhone 4's HDR functionality is a handy tool to have on board. It can be useful in certain situations but the key is to know when — and why — to activate it. We hope this article has helped, but with almost all photography the best way to get familar with the tech is to shoot as much as you can — so grab your iPhone, get out there and get snapping!