Apple adds HDR to new iPhone OS

Apple made some new announcements at their Apple Fall 2010 event, and if you’re an Apple aficionado, you’re going to want to check out the whole thing over at Engadget.

However, one of the things that Apple mentioned is that Apple iPhone 4 users will soon be able to take High Dynamic Range photographs.

You’ve probably seen, or at least heard of, High Dynamic Range photography. At its simplest, high dynamic range photography combines otherwise identical shots that have been taken with differences in exposure, and then composite the photographs into a single photograph which shows details in both highlights and shadows.

In any photo medium, there will be a point at which there will be something “too dark” to make out any detail, and a point at which something will be “too bright” to make out any detail. You could make the picture “brighter” and bring more details to the shadows, but then more bright spots will end up “too bright,” (or outside the dynamic range.) Similarly, capturing more bright detail means you lose more in darkness.

Think about taking a picture through a sunny window in a dim room. If the room looks good in the camera, chances are the window will be blown out; if the window looks fine, the room will be too dark to make out details.

The “distance” between “too dark” and “too bright,” as measured in “stops” of light, is the dynamic range. A point-and-click digital camera may have a small dynamic range – perhaps 8 stops of dynamic range or so. High-end SLR cameras tend to have around 10-11 stops of dynamic range. And film tends to have the highest dynamic range at around 14 stops of light.

What high dynamic range photographs are, essentially, are a computerized “cheat” to get around the limitations of dynamic range. While it would not work with a moving subject, photographers can take photos at different exposure levels (usually, but not always, by changing a digital camera’s ISO light sensitivity rating). By combining the 11 stops of dynamic range from the dark picture, and overlapping those details in the shadows with the 11 stops of dynamic range you’d get from the bright picture, with details in the highlights, you can composite a picture with the details of both.

Of course, to get the best results, you typically had to painstakingly line up the shot, manually edit camera settings, and usually use a tripod to keep the camera steady – after all, any movement, and the computer won’t be able to composite the shot correctly.

Putting HDR into the iPhone is a smart move for boosting the iPhone’s photography abilities. Typically cameras with smaller sensors (and the iPhone, being a compact, portable device, has a very small one) have tended to have less dynamic range than even dedicated point-and-shoot cameras. They also tended to gather less light as a whole, requiring longer exposure times than most cameras. Adding a built-in HDR ability makes the iPhone’s photographic capability, assuming Apple can find a way to keep shaking and blurring to a minimum, might make Apple’s camera-phone from a “nice to have” to a real professional alternative for taking photographs. Well, at least in a pinch.


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