First look: HDR cranks up the awesome factor on your iPhone 4′s camera: but is it real HDR?

Spot the new setting?

One of the nice surprises at today’s Apple event was the addition of HDR (high dynamic range) to the camera app on the iPhone 4 in iOS 4.1. HDR is a photographic technique that blends together three photos taken at various levels of exposure and combines the best of all of them into one. A good explanation can be found on this site, but the result is a shot that captures both the shadows and the bright parts of a picture without washing out and detail. We’ve downloaded the 4.1 GM today and taken a few shots to put it through its paces.

Using HDR on the iPhone is just as easy as you’d imagine — on the camera UI there is now a ‘HDR on’ button at the top of the viewfinder. Tap it to turn it on or off. In the Settings app under Photos, you can choose whether or not to keep the original shot as well as the HDR shot when you have it turned on.

This is HDR (but not from an iPhone!)

HDR isn’t useful for all types of shot, so you won’t necessarily want to leave it switched on all the time. It’s most useful for shots that capture the extremes of light and dark — for example, pictures of looking out a window where normally either the inside part would be drowned in darkness or the outside part would be nothing but a bright white blur are dramatically improved with HDR.

To show you what I mean, take the below photos. This was taken looking along a fairly dark hallway towards a large arched, lead-light window. The first two photos were taken with the ‘normal’ camera mode. In photo one, I tapped the window to adjust the exposure to the brightest part of the frame. You can make out the lead-lighting on the window and what’s beyond it, but the hallway itself is lost in shadow.

Photo 1: Tapping on the window

In photo two, I tapped on the darkest part of the frame so that the exposure level was adjusted to show the detail there. You’ll notice that you can no longer make out the lead-lighting and the window is just a mess.

Photo 2: Tapping on the darkened areas

The third photo was taken with HDR mode switched on, and you’ll see that it’s a perfect combination of the best of all modes. The view out the window can be made-out, the lead-lighting can be seen, and the colour and detail of the wood in the hallway can be made out.

Photo 3: HDR mode

Here are some more HDR shots that demonstrate a similar situation.

Left: HDR off, Right: HDR on.

Notice in the original on the left the car’s bonnet and the garage’s roof is lost in shimmering white, and the detail of the flowers and inside the glass vase is too dark to make out. On the HDR shot, this is all balanced.

Left: HDR off, Right: HDR on

Note that in the original shot on the left you cannot make out the view through the furthest window and the wood (particularly at the top of the shot) is in darkness. Again, with HDR switched on detail can be seen and brightness is balanced.

Now here’s the strange bit: because true HDR is a combination of three different shots, theoretically it should only works with still subjects. If you try to take a picture where there is movement in the frame, you should end up with a blurry mess. But somehow, the result is not a blurry mess at all. I took a number of shots with my dog, and I was purposefully panning and moving the camera when I took it, just to see what would happen. The result: a completely still HDR scene.

Good boy! Left: Original, Right: HDR

Take the above for example. My dog does not sit still, and to make it harder for the iPhone I was purposefully moving the camera while it took these shots. I was expecting the result to be a combination of my dog in three slightly different positions all ghosted on top of each other. But you’ll see that didn’t happen.

Couple this with the fact that it also saves both the HDR shot and only one original rather than three, and I’m left wondering whether this is actually true HDR or a software effect along the lines of the ‘Enhance’ button in iPhoto.

If anybody has any insights into this, let us know. But in the meantime: what do you think? Like it? Hate it? See a use for it? Let us know in the comments!